'Unfortunately, TimeoutMixin does not allow passing an explicit reactor
to test timeouts. For that reason, we need to monkeypatch the method
set up by the TimeoutMixin.
@param connection: The HTTP/2 connection object to patch.
@type connection: L{H2Connection}
@param reactor: The reactor whose callLater method we want.
@type reactor: An object implementing
L{twisted.internet.interfaces.IReactorTime}'

def patch_TimeoutMixin_clock(self, connection, reactor):

    connection.callLater = reactor.callLater
