Fixed #24257 -- Corrected i18n handling of percent signs.

Refactored tests to use a sample project.

Updated extraction:
* Removed special handling of single percent signs.
* When extracting messages from template text, doubled all percent signs
  so they are not interpreted by gettext as string format flags. All
  strings extracted by gettext, if containing a percent sign, will now
  be labeled "#, python-format".

Updated translation:
* Used "%%" for "%" in template text before calling gettext.
* Updated {% trans %} rendering to restore "%" from "%%".

1 files changed, 6 insertions, 0 deletions

diff --git a/django/templatetags/i18n.py b/django/templatetags/i18n.py
index 4e77aaece4..050ef2c741 100644
--- a/django/templatetags/i18n.py
+++ b/django/templatetags/i18n.py
@@ -7,6 +7,7 @@ from django.template import Library, Node, TemplateSyntaxError, Variable
 from django.template.base import TOKEN_TEXT, TOKEN_VAR, render_value_in_context
 from django.template.defaulttags import token_kwargs
 from django.utils import six, translation
+from django.utils.safestring import SafeData, mark_safe
 
 register = Library()
 
@@ -86,6 +87,11 @@ class TranslateNode(Node):
                 self.message_context.resolve(context))
         output = self.filter_expression.resolve(context)
         value = render_value_in_context(output, context)
+        # Restore percent signs. Percent signs in template text are doubled
+        # so they are not interpreted as string format flags.
+        is_safe = isinstance(value, SafeData)
+        value = value.replace('%%', '%')
+        value = mark_safe(value) if is_safe else value
         if self.asvar:
             context[self.asvar] = value
             return ''