Create a new empty migration.

def create(self, name):
        """Create a new empty migration."""
        if not os.path.exists(self.directory):
            os.makedirs(self.directory)

        filename = self.get_new_filename(name)
        with open(os.path.join(self.directory, filename), 'w') as fp:
            fp.write("def up(db): pass\n\n\n")
            fp.write("def down(db): pass\n")
            logger.info(filename)