Edited model and field checks for grammar and consistency.

4 files changed, 122 insertions, 126 deletions

diff --git a/django/core/checks/model_checks.py b/django/core/checks/model_checks.py
index 3110d7c491..7029317324 100644
--- a/django/core/checks/model_checks.py
+++ b/django/core/checks/model_checks.py
@@ -36,14 +36,14 @@ def check_model_signals(app_configs=None, **kwargs):
                         description = "An instance of the `%s` class" % receiver.__class__.__name__
                     errors.append(
                         Error(
-                            "%s was connected to the `%s` signal "
+                            "%s was connected to the '%s' signal "
                             "with a lazy reference to the '%s' sender, "
                             "which has not been installed." % (
                                 description, name, '.'.join(reference)
                             ),
                             obj=receiver.__module__,
                             hint=None,
-                            id='E014'
+                            id='signals.E001'
                         )
                     )
     return errors
diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index e2fef7fb71..be1f237b12 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -197,10 +197,10 @@ class Field(RegisterLookupMixin):
         if self.name.endswith('_'):
             return [
                 checks.Error(
-                    'Field names must not end with underscores.',
+                    'Field names must not end with an underscore.',
                     hint=None,
                     obj=self,
-                    id='E001',
+                    id='fields.E001',
                 )
             ]
         elif '__' in self.name:
@@ -209,16 +209,16 @@ class Field(RegisterLookupMixin):
                     'Field names must not contain "__".',
                     hint=None,
                     obj=self,
-                    id='E052',
+                    id='fields.E002',
                 )
             ]
         elif self.name == 'pk':
             return [
                 checks.Error(
-                    'Cannot use "pk" as a field name since it is a reserved name.',
+                    "'pk' is a reserved word that cannot be used as a field name.",
                     hint=None,
                     obj=self,
-                    id='E051',
+                    id='fields.E003',
                 )
             ]
         else:
@@ -230,10 +230,10 @@ class Field(RegisterLookupMixin):
                     not is_iterable(self.choices)):
                 return [
                     checks.Error(
-                        '"choices" must be an iterable (e.g., a list or tuple).',
+                        "'choices' must be an iterable (e.g., a list or tuple).",
                         hint=None,
                         obj=self,
-                        id='E033',
+                        id='fields.E004',
                     )
                 ]
             elif any(isinstance(choice, six.string_types) or
@@ -241,13 +241,11 @@ class Field(RegisterLookupMixin):
                      for choice in self.choices):
                 return [
                     checks.Error(
-                        ('All "choices" elements must be a tuple of two '
-                         'elements (the first one is the actual value '
-                         'to be stored and the second element is '
-                         'the human-readable name).'),
+                        ("'choices' must be an iterable containing "
+                         "(actual value, human readable name) tuples."),
                         hint=None,
                         obj=self,
-                        id='E034',
+                        id='fields.E005',
                     )
                 ]
             else:
@@ -259,10 +257,10 @@ class Field(RegisterLookupMixin):
         if self.db_index not in (None, True, False):
             return [
                 checks.Error(
-                    '"db_index" must be either None, True or False.',
+                    "'db_index' must be None, True or False.",
                     hint=None,
                     obj=self,
-                    id='E035',
+                    id='fields.E006',
                 )
             ]
         else:
@@ -277,10 +275,10 @@ class Field(RegisterLookupMixin):
             return [
                 checks.Error(
                     'Primary keys must not have null=True.',
-                    hint=('Set null=False on the field or '
+                    hint=('Set null=False on the field, or '
                           'remove primary_key=True argument.'),
                     obj=self,
-                    id='E036',
+                    id='fields.E007',
                 )
             ]
         else:
@@ -864,10 +862,10 @@ class AutoField(Field):
         if not self.primary_key:
             return [
                 checks.Error(
-                    'The field must have primary_key=True, because it is an AutoField.',
+                    'AutoFields must set primary_key=True.',
                     hint=None,
                     obj=self,
-                    id='E048',
+                    id='fields.E100',
                 ),
             ]
         else:
@@ -940,10 +938,10 @@ class BooleanField(Field):
         if getattr(self, 'null', False):
             return [
                 checks.Error(
-                    'BooleanFields do not acceps null values.',
+                    'BooleanFields do not accept null values.',
                     hint='Use a NullBooleanField instead.',
                     obj=self,
-                    id='E037',
+                    id='fields.E110',
                 )
             ]
         else:
@@ -1020,19 +1018,19 @@ class CharField(Field):
         except TypeError:
             return [
                 checks.Error(
-                    'The field must have "max_length" attribute.',
+                    "CharFields must define a 'max_length' attribute.",
                     hint=None,
                     obj=self,
-                    id='E038',
+                    id='fields.E120',
                 )
             ]
         except ValueError:
             return [
                 checks.Error(
-                    '"max_length" must be a positive integer.',
+                    "'max_length' must be a positive integer.",
                     hint=None,
                     obj=self,
-                    id='E039',
+                    id='fields.E121',
                 )
             ]
         else:
@@ -1305,24 +1303,16 @@ class DecimalField(Field):
 
     def check(self, **kwargs):
         errors = super(DecimalField, self).check(**kwargs)
-        errors.extend(self._check_decimal_places_and_max_digits(**kwargs))
-        return errors
 
-    def _check_decimal_places_and_max_digits(self, **kwargs):
-        errors = self.__check_decimal_places()
-        errors += self.__check_max_digits()
-        if not errors and int(self.decimal_places) > int(self.max_digits):
-            errors.append(
-                checks.Error(
-                    '"max_digits" must be greater or equal to "decimal_places".',
-                    hint=None,
-                    obj=self,
-                    id='E040',
-                )
-            )
+        digits_errors = self._check_decimal_places()
+        digits_errors.extend(self._check_max_digits())
+        if not digits_errors:
+            errors.extend(self._check_decimal_places_and_max_digits(**kwargs))
+        else:
+            errors.extend(digits_errors)
         return errors
 
-    def __check_decimal_places(self):
+    def _check_decimal_places(self):
         try:
             decimal_places = int(self.decimal_places)
             if decimal_places < 0:
@@ -1330,25 +1320,25 @@ class DecimalField(Field):
         except TypeError:
             return [
                 checks.Error(
-                    'The field requires a "decimal_places" attribute.',
+                    "DecimalFields must define a 'decimal_places' attribute.",
                     hint=None,
                     obj=self,
-                    id='E041',
+                    id='fields.E130',
                 )
             ]
         except ValueError:
             return [
                 checks.Error(
-                    '"decimal_places" attribute must be a non-negative integer.',
+                    "'decimal_places' must be a non-negative integer.",
                     hint=None,
                     obj=self,
-                    id='E042',
+                    id='fields.E131',
                 )
             ]
         else:
             return []
 
-    def __check_max_digits(self):
+    def _check_max_digits(self):
         try:
             max_digits = int(self.max_digits)
             if max_digits <= 0:
@@ -1356,24 +1346,36 @@ class DecimalField(Field):
         except TypeError:
             return [
                 checks.Error(
-                    'The field requires a "max_digits" attribute.',
+                    "DecimalFields must define a 'max_digits' attribute.",
                     hint=None,
                     obj=self,
-                    id='E043',
+                    id='fields.E132',
                 )
             ]
         except ValueError:
             return [
                 checks.Error(
-                    '"max_digits" attribute must be a positive integer.',
+                    "'max_digits' must be a positive integer.",
                     hint=None,
                     obj=self,
-                    id='E044',
+                    id='fields.E133',
                 )
             ]
         else:
             return []
 
+    def _check_decimal_places_and_max_digits(self, **kwargs):
+        if int(self.decimal_places) > int(self.max_digits):
+            return [
+                checks.Error(
+                    "'max_digits' must be greater or equal to 'decimal_places'.",
+                    hint=None,
+                    obj=self,
+                    id='fields.E134',
+                )
+            ]
+        return []
+
     def deconstruct(self):
         name, path, args, kwargs = super(DecimalField, self).deconstruct()
         if self.max_digits:
@@ -1481,10 +1483,10 @@ class FilePathField(Field):
         if not self.allow_files and not self.allow_folders:
             return [
                 checks.Error(
-                    'The field must have either "allow_files" or "allow_folders" set to True.',
+                    "FilePathFields must have either 'allow_files' or 'allow_folders' set to True.",
                     hint=None,
                     obj=self,
-                    id='E045',
+                    id='fields.E140',
                 )
             ]
         return []
@@ -1659,11 +1661,11 @@ class GenericIPAddressField(Field):
         if not getattr(self, 'null', False) and getattr(self, 'blank', False):
             return [
                 checks.Error(
-                    ('The field cannot accept blank values if null values '
-                     'are not allowed, as blank values are stored as null.'),
+                    ('GenericIPAddressFields cannot have blank=True if null=False, '
+                     'as blank values are stored as nulls.'),
                     hint=None,
                     obj=self,
-                    id='E046',
+                    id='fields.E150',
                 )
             ]
         return []
diff --git a/django/db/models/fields/files.py b/django/db/models/fields/files.py
index 4a19fe9052..9d4a06daca 100644
--- a/django/db/models/fields/files.py
+++ b/django/db/models/fields/files.py
@@ -246,10 +246,10 @@ class FileField(Field):
         if self._unique_set_explicitly:
             return [
                 checks.Error(
-                    '"unique" is not a valid argument for %s.' % self.__class__.__name__,
+                    "'unique' is not a valid argument for a %s." % self.__class__.__name__,
                     hint=None,
                     obj=self,
-                    id='E049',
+                    id='fields.E200',
                 )
             ]
         else:
@@ -259,10 +259,10 @@ class FileField(Field):
         if self._primary_key_set_explicitly:
             return [
                 checks.Error(
-                    '"primary_key" is not a valid argument for %s.' % self.__class__.__name__,
+                    "'primary_key' is not a valid argument for a %s." % self.__class__.__name__,
                     hint=None,
                     obj=self,
-                    id='E050',
+                    id='fields.E201',
                 )
             ]
         else:
@@ -392,11 +392,11 @@ class ImageField(FileField):
         except ImproperlyConfigured:
             return [
                 checks.Error(
-                    'To use ImageFields, Pillow must be installed.',
+                    'Cannot use ImageField because Pillow is not installed.',
                     hint=('Get Pillow at https://pypi.python.org/pypi/Pillow '
                           'or run command "pip install pillow".'),
                     obj=self,
-                    id='E032',
+                    id='fields.E210',
                 )
             ]
         else:
diff --git a/django/db/models/fields/related.py b/django/db/models/fields/related.py
index 3c022d6fcc..aef26444f0 100644
--- a/django/db/models/fields/related.py
+++ b/django/db/models/fields/related.py
@@ -108,13 +108,11 @@ class RelatedField(Field):
         if rel_is_missing and (rel_is_string or not self.rel.to._meta.swapped):
             return [
                 checks.Error(
-                    ('The field has a relation with model %s, which '
-                     'has either not been installed or is abstract.') % model_name,
-                    hint=('Ensure that you did not misspell the model name and '
-                          'the model is not abstract. Does your INSTALLED_APPS '
-                          'setting contain the app where %s is defined?') % model_name,
+                    ("Field defines a relation with model '%s', which "
+                     "is either not installed, or is abstract.") % model_name,
+                    hint=None,
                     obj=self,
-                    id='E030',
+                    id='fields.E300',
                 )
             ]
         return []
@@ -129,11 +127,11 @@ class RelatedField(Field):
             )
             return [
                 checks.Error(
-                    ('The field defines a relation with the model %s, '
-                     'which has been swapped out.') % model,
-                    hint='Update the relation to point at settings.%s' % self.rel.to._meta.swappable,
+                    ("Field defines a relation with the model '%s', "
+                     "which has been swapped out.") % model,
+                    hint="Update the relation to point at 'settings.%s'." % self.rel.to._meta.swappable,
                     obj=self,
-                    id='E029',
+                    id='fields.E301',
                 )
             ]
         return []
@@ -190,22 +188,22 @@ class RelatedField(Field):
             if clash_field.name == rel_name:
                 errors.append(
                     checks.Error(
-                        'Accessor for field %s clashes with field %s.' % (field_name, clash_name),
-                        hint=('Rename field %s or add/change a related_name '
-                              'argument to the definition for field %s.') % (clash_name, field_name),
+                        "Reverse accessor for '%s' clashes with field name '%s'." % (field_name, clash_name),
+                        hint=("Rename field '%s', or add/change a related_name "
+                              "argument to the definition for field '%s'.") % (clash_name, field_name),
                         obj=self,
-                        id='E014',
+                        id='fields.E302',
                     )
                 )
 
             if clash_field.name == rel_query_name:
                 errors.append(
                     checks.Error(
-                        'Reverse query name for field %s clashes with field %s.' % (field_name, clash_name),
-                        hint=('Rename field %s or add/change a related_name '
-                              'argument to the definition for field %s.') % (clash_name, field_name),
+                        "Reverse query name for '%s' clashes with field name '%s'." % (field_name, clash_name),
+                        hint=("Rename field '%s', or add/change a related_name "
+                              "argument to the definition for field '%s'.") % (clash_name, field_name),
                         obj=self,
-                        id='E015',
+                        id='fields.E303',
                     )
                 )
 
@@ -223,22 +221,22 @@ class RelatedField(Field):
             if clash_field.get_accessor_name() == rel_name:
                 errors.append(
                     checks.Error(
-                        'Clash between accessors for %s and %s.' % (field_name, clash_name),
-                        hint=('Add or change a related_name argument '
-                              'to the definition for %s or %s.') % (field_name, clash_name),
+                        "Reverse accessor for '%s' clashes with reverse accessor for '%s'." % (field_name, clash_name),
+                        hint=("Add or change a related_name argument "
+                              "to the definition for '%s' or '%s'.") % (field_name, clash_name),
                         obj=self,
-                        id='E016',
+                        id='fields.E304',
                     )
                 )
 
             if clash_field.get_accessor_name() == rel_query_name:
                 errors.append(
                     checks.Error(
-                        'Clash between reverse query names for %s and %s.' % (field_name, clash_name),
-                        hint=('Add or change a related_name argument '
-                              'to the definition for %s or %s.') % (field_name, clash_name),
+                        "Reverse query name for '%s' clashes with reverse query name for '%s'." % (field_name, clash_name),
+                        hint=("Add or change a related_name argument "
+                              "to the definition for '%s' or '%s'.") % (field_name, clash_name),
                         obj=self,
-                        id='E017',
+                        id='fields.E305',
                     )
                 )
 
@@ -1317,17 +1315,15 @@ class ForeignObject(RelatedField):
         has_unique_field = any(rel_field.unique
             for rel_field in self.foreign_related_fields)
         if not has_unique_field and len(self.foreign_related_fields) > 1:
-            field_combination = ','.join(rel_field.name
+            field_combination = ', '.join("'%s'" % rel_field.name
                 for rel_field in self.foreign_related_fields)
             model_name = self.rel.to.__name__
             return [
                 checks.Error(
-                    ('No unique=True constraint '
-                     'on field combination "%s" under model %s.') % (field_combination, model_name),
-                    hint=('Set unique=True argument on any of the fields '
-                          '"%s" under model %s.') % (field_combination, model_name),
+                    "None of the fields %s on model '%s' have a unique=True constraint." % (field_combination, model_name),
+                    hint=None,
                     obj=self,
-                    id='E018',
+                    id='fields.E310',
                 )
             ]
         elif not has_unique_field:
@@ -1335,11 +1331,11 @@ class ForeignObject(RelatedField):
             model_name = self.rel.to.__name__
             return [
                 checks.Error(
-                    ('%s.%s must have unique=True '
-                     'because it is referenced by a foreign key.') % (model_name, field_name),
+                    ("'%s.%s' must set unique=True "
+                     "because it is referenced by a foreign key.") % (model_name, field_name),
                     hint=None,
                     obj=self,
-                    id='E019',
+                    id='fields.E311',
                 )
             ]
         else:
@@ -1605,19 +1601,19 @@ class ForeignKey(ForeignObject):
         if on_delete == SET_NULL and not self.null:
             return [
                 checks.Error(
-                    'The field specifies on_delete=SET_NULL, but cannot be null.',
-                    hint='Set null=True argument on the field.',
+                    'Field specifies on_delete=SET_NULL, but cannot be null.',
+                    hint='Set null=True argument on the field, or change the on_delete rule.',
                     obj=self,
-                    id='E020',
+                    id='fields.E320',
                 )
             ]
         elif on_delete == SET_DEFAULT and not self.has_default():
             return [
                 checks.Error(
-                    'The field specifies on_delete=SET_DEFAULT, but has no default value.',
-                    hint=None,
+                    'Field specifies on_delete=SET_DEFAULT, but has no default value.',
+                    hint='Set a default value, or change the on_delete rule.',
                     obj=self,
-                    id='E021',
+                    id='fields.E321',
                 )
             ]
         else:
@@ -1864,10 +1860,10 @@ class ManyToManyField(RelatedField):
         if self.unique:
             return [
                 checks.Error(
-                    'ManyToManyFields must not be unique.',
+                    'ManyToManyFields cannot be unique.',
                     hint=None,
                     obj=self,
-                    id='E022',
+                    id='fields.E330',
                 )
             ]
         return []
@@ -1879,13 +1875,11 @@ class ManyToManyField(RelatedField):
             # The relationship model is not installed.
             errors.append(
                 checks.Error(
-                    ('The field specifies a many-to-many relation through model '
-                     '%s, which has not been installed.') % self.rel.through,
-                    hint=('Ensure that you did not misspell the model name and '
-                          'the model is not abstract. Does your INSTALLED_APPS '
-                          'setting contain the app where %s is defined?') % self.rel.through,
+                    ("Field specifies a many-to-many relation through model "
+                     "'%s', which has not been installed.") % self.rel.through,
+                    hint=None,
                     obj=self,
-                    id='E023',
+                    id='fields.E331',
                 )
             )
 
@@ -1914,7 +1908,7 @@ class ManyToManyField(RelatedField):
                         'Many-to-many fields with intermediate tables must not be symmetrical.',
                         hint=None,
                         obj=self,
-                        id='E024',
+                        id='fields.E332',
                     )
                 )
 
@@ -1926,12 +1920,12 @@ class ManyToManyField(RelatedField):
                 if seen_self > 2:
                     errors.append(
                         checks.Error(
-                            ('The model is used as an intermediary model by '
-                             '%s, but it has more than two foreign keys '
-                             'to %s, which is ambiguous and is not permitted.') % (self, from_model_name),
+                            ("The model is used as an intermediate model by "
+                             "'%s', but it has more than two foreign keys "
+                             "to '%s', which is ambiguous.") % (self, from_model_name),
                             hint=None,
                             obj=self.rel.through,
-                            id='E025',
+                            id='fields.E333',
                         )
                     )
 
@@ -1945,41 +1939,41 @@ class ManyToManyField(RelatedField):
                 if seen_from > 1:
                     errors.append(
                         checks.Error(
-                            ('The model is used as an intermediary model by '
-                             '%s, but it has more than one foreign key '
-                             'to %s, which is ambiguous and is not permitted.') % (self, from_model_name),
+                            ("The model is used as an intermediate model by "
+                             "'%s', but it has more than one foreign key "
+                             "from '%s', which is ambiguous.") % (self, from_model_name),
                             hint=('If you want to create a recursive relationship, '
                                   'use ForeignKey("self", symmetrical=False, '
                                   'through="%s").') % relationship_model_name,
                             obj=self,
-                            id='E026',
+                            id='fields.E334',
                         )
                     )
 
                 if seen_to > 1:
                     errors.append(
                         checks.Error(
-                            ('The model is used as an intermediary model by '
-                             '%s, but it has more than one foreign key '
-                             'to %s, which is ambiguous and is not permitted.') % (self, to_model_name),
+                            ("The model is used as an intermediate model by "
+                             "'%s', but it has more than one foreign key "
+                             "to '%s', which is ambiguous.") % (self, to_model_name),
                             hint=('If you want to create a recursive '
                                   'relationship, use ForeignKey("self", '
                                   'symmetrical=False, through="%s").') % relationship_model_name,
                             obj=self,
-                            id='E027',
+                            id='fields.E335',
                         )
                     )
 
                 if seen_from == 0 or seen_to == 0:
                     errors.append(
                         checks.Error(
-                            ('The model is used as an intermediary model by '
-                             '%s, but it misses a foreign key to %s or %s.') % (
+                            ("The model is used as an intermediate model by "
+                             "'%s', but it does not have a foreign key to '%s' or '%s'.") % (
                                 self, from_model_name, to_model_name
                             ),
                             hint=None,
                             obj=self.rel.through,
-                            id='E028',
+                            id='fields.E336',
                         )
                     )
         return errors