Releases the connection back to the pool.

def release(self, connection):
        "Releases the connection back to the pool."
        # Make sure we haven't changed process.
        self._checkpid()
        if connection.pid != self.pid:
            return

        # Put the connection back into the pool.
        try:
            self.pool.put_nowait(connection)
        except Full:
            # perhaps the pool has been reset() after a fork? regardless,
            # we don't want this connection
            pass