Returns a name of a new migration. It will usually be a filename with
        a valid and unique name.

        :param name: human-readable name of a migration
        :param suffix: file suffix (extension) - eg. 'sql'

def generate_migration_name(self, name, suffix):
        """Returns a name of a new migration. It will usually be a filename with
        a valid and unique name.

        :param name: human-readable name of a migration
        :param suffix: file suffix (extension) - eg. 'sql'
        """
        return os.path.join(self.dir,
                            'm{datestr}_{name}.{suffix}'.format(
                                datestr=datetime.datetime.utcnow().strftime('%Y%m%d%H%M%S'),
                                name=name.replace(' ', '_'),
                                suffix=suffix))