Get connection from pool and execute transaction.

def _ExecuteTransaction(self, transaction):
    """Get connection from pool and execute transaction."""

    def Action(connection):
      connection.cursor.execute("START TRANSACTION")
      for query in transaction:
        connection.cursor.execute(query["query"], query["args"])
      connection.cursor.execute("COMMIT")
      return connection.cursor.fetchall()

    return self._RetryWrapper(Action)