Possibly fix an infinite recursion crash by avoid str() inside repr()

See https://code.djangoproject.com/ticket/33134

Author: matthiask

tests/forms.py

@@ -6,4 +6,4 @@ class TemplateReprForm(forms.Form):
     user = forms.ModelChoiceField(queryset=User.objects.all())
 
     def __repr__(self):
-        return str(self)
+        return repr(self)