code: def generate_migration_name(self, name, suffix):
          
          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))
docs: 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'