'Add a city field to a form description.
Arguments:
form_desc: A form description
Keyword Arguments:
required (bool): Whether this field is required; defaults to True'

def _add_city_field(self, form_desc, required=True):

    city_label = _(u'City')
    error_msg = accounts.REQUIRED_FIELD_CITY_MSG
    form_desc.add_field('city', label=city_label, required=required, error_messages={'required': error_msg})
