You just have to do some rearangements:
class ClientForm(ModelForm):
def __init__(self, *args, **kwargs):
kwargs.update({'error_class': jQueryUiErrors})
super(ClientForm, self).__init__(*args, **kwargs)
class Meta:
model = Client
fields = ['first_name', 'last_name', 'owner', 'source', 'contact_status', 'next_contact']
Or:
class ClientForm(ModelForm):
def __init__(self, *args, **kwargs):
super(ClientForm, self).__init__(*args, **kwargs)
self.error_class = jQueryUiErrors