Django: TemplateSyntaxError at /admin/foo/bar/30/ Caught an exception while rendering: ‘ascii’ codec can’t encode character u’\u201d’ in position 3: ordinal not in range(128)

I recently ran into this error with an old Django site.
TemplateSyntaxError at /admin/foo/bar/30/
Caught an exception while rendering: 'ascii' codec can't encode character u'\u201d' in position 3: ordinal not in range(128)
Make sure that you're defining __unicode__ methods on your models and not __str__!
This fixed the problem for me.