When you try to use a blocktrans with a percent sign in it. When the percent is escaped (%%) it renders fine. It does not occur when using a trans tag.
>>> from django.template import Context, Template
>>> t1 = Template('{% load i18n %}{% blocktrans %}We lost 5% today.{% endblocktrans %}')
>>> t2 = Template('{% load i18n %}{% blocktrans %}We lost 5%% today.{% endblocktrans %}')
>>> t3 = Template('{% load i18n %}{% trans "We lost 5% today." %}')
>>> c = Context()
>>> t1.render(c)
Traceback (most recent call last):
File "<console>", line 1, in <module>
File "D:\Python\lib\site-packages\django\template\__init__.py", line 181, in render
return self.nodelist.render(context)
File "D:\Python\lib\site-packages\django\template\__init__.py", line 736, in render
bits.append(self.render_node(node, context))
File "D:\Python\lib\site-packages\django\template\__init__.py", line 764, in render_node
raise wrapped
TemplateSyntaxError: Caught an exception while rendering: unsupported format character 't' (0x74) at index 11
Original Traceback (most recent call last):
File "D:\Python\lib\site-packages\django\template\__init__.py", line 754, in render_node
result = node.render(context)
File "D:\Python\lib\site-packages\django\templatetags\i18n.py", line 73, in render
result = translation.ugettext(singular) % context
ValueError: unsupported format character 't' (0x74) at index 11
>>> t2.render(c)
u'We lost 5% today.'
>>> t3.render(c)
u'We lost 5% today.'
