Overriding form field error messages without argument causes string formatting error.

[klein4]

Something like this in a form's init method

self.fields['my_choice_field'].error_messages['invalid_choice'] = u'Constant string'

will throw an error because of the following line in django/forms/models.py (line 1015):

raise ValidationError(self.error_messages['invalid_choice'] % val)

This method of string formatting forces the user's custom error message to contain a '%s' argument, like the default error message does. A dictionary-based string formatting operation like

self.error_messages['invalid_choice'] % {'foo': bar}

would fix this problem.

[Claude Paroz]

Now that the 1.4 branch is string-frozen, this will have to wait for 1.5.

[Claude Paroz]

I understand that this patch might be slightly backwards incompatible, but I think this needs to be fixed.

[Claude Paroz]

See also #19832

[Claude Paroz]

Added ungettext_lazy for some messages

[Claude Paroz]

I updated the patch to include issues of ticket #19832.

[Claude Paroz <claude@…>]

In be9ae693c46021fd3a70c0ec21dd566960b29ffb:

Fixed #17840 -- Generalized named placeholders in form error messages

Also fixed plural messages for DecimalField.

[Claude Paroz <claude@…>]

In 5306285ce21d59742d67a447c9c1a1e4be6d86a4:

Complemented documentation following commit be9ae693c

Refs #17840. Thanks Carl Meyer for noticing the omission.