Fixed #27258 -- Prohibited django.Template.render() with non-dict context.

Thanks Shivang Bharadwaj for the initial patch.

docs/releases/1.11.txt

@@ -575,6 +575,15 @@ Some undocumented classes in ``django.forms.widgets`` are removed:
 The ``Widget.format_output()`` method is removed. Use a custom widget template
 instead.
 
+``django.Template.render()`` prohibits non-dict context
+-------------------------------------------------------
+
+For compatibility with multiple template engines, ``django.Template.render()``
+must receive a dictionary of context rather than ``Context`` or
+``RequestContext``. If you were passing either of the two classes, pass a
+dictionary instead -- doing so is backwards-compatible with older versions of
+Django.
+
 Miscellaneous
 -------------