Assert that value in JSONFormField is a string or None.
Assert that value in JSONFormField is a string or None.

* there is a chance that if we use custom widgets for the field, we
might end up with non-string value, which is wrong. This assert will
help identify potential issues. JSONFormField expects text or None only
and if we provide anything else (i.e. dictionary) we will have assertion
error raised very quickly.

grzes/djangae,potatolondon/djangae,grzes/djangae,potatolondon/djangae,grzes/djangae