'Returns a field\'s type suitable for ALTER COLUMN.
By default it just returns field.db_type().
To be overriden by backend specific subclasses
@param field: The field to generate type for'

def _db_type_for_alter_column(self, field):

    try:
        return field.db_type(connection=self._get_connection())
    except TypeError:
        return field.db_type()
