Fixed #16905 -- Added extensible checks (nee validation) framework

This is the result of Christopher Medrela's 2013 Summer of Code project.

Thanks also to Preston Holmes, Tim Graham, Anssi Kääriäinen, Florian
Apolloner, and Alex Gaynor for review notes along the way.

Also: Fixes #8579, fixes #3055, fixes #19844.

1 files changed, 12 insertions, 4 deletions

diff --git a/django/forms/models.py b/django/forms/models.py
index a8494360c2..7c4c92c140 100644
--- a/django/forms/models.py
+++ b/django/forms/models.py
@@ -927,9 +927,13 @@ def _get_foreign_key(parent_model, model, fk_name=None, can_fail=False):
             if not isinstance(fk, ForeignKey) or \
                     (fk.rel.to != parent_model and
                      fk.rel.to not in parent_model._meta.get_parent_list()):
-                raise Exception("fk_name '%s' is not a ForeignKey to %s" % (fk_name, parent_model))
+                raise ValueError(
+                    "fk_name '%s' is not a ForeignKey to '%s.%'."
+                    % (fk_name, parent_model._meta.app_label, parent_model._meta.object_name))
         elif len(fks_to_parent) == 0:
-            raise Exception("%s has no field named '%s'" % (model, fk_name))
+            raise ValueError(
+                "'%s.%s' has no field named '%s'."
+                % (model._meta.app_label, model._meta.object_name, fk_name))
     else:
         # Try to discover what the ForeignKey from model to parent_model is
         fks_to_parent = [
@@ -943,9 +947,13 @@ def _get_foreign_key(parent_model, model, fk_name=None, can_fail=False):
         elif len(fks_to_parent) == 0:
             if can_fail:
                 return
-            raise Exception("%s has no ForeignKey to %s" % (model, parent_model))
+            raise ValueError(
+                "'%s.%s' has no ForeignKey to '%s.%s'."
+                % (model._meta.app_label, model._meta.object_name, parent_model._meta.app_label, parent_model._meta.object_name))
         else:
-            raise Exception("%s has more than 1 ForeignKey to %s" % (model, parent_model))
+            raise ValueError(
+                "'%s.%s' has more than one ForeignKey to '%s.%s'."
+                % (model._meta.app_label, model._meta.object_name, parent_model._meta.app_label, parent_model._meta.object_name))
     return fk