twisted.conch.ssh.factory.SSHFactory.buildProtocol doesn't let you customize the protocol it creates

[mwh]

We want to set tcp keepalives on all connections to our ssh server, which would seem to be most logically done in connectionMade of the protocol object created on a connection -- but there's no way to influence the class of the protocol object created here, other than copy-paste-hacking buildProtocol into your factory subclass.

If SSHFactory.buildProtocol delegated to Factory.buildProtocol, you could do it by defining 'protocol' in your factory subclass, as in most of the rest of Twisted.

Diff attached, no tests though.

[jml]

If you want to test this (and you do), then probably the best thing to do is add a 'test_factory' file to t/conch/tests, and then demonstrate that calls to buildProtocol call self.protocol with the correct parameters.

It might even be ok to just check that the return value of buildProtocol is an instance of self.protocol.

[mwh]

How does this look?

[jml]

• Need two lines of vertical whitespace between methods
• Use docstrings rather than comments for tests: """\nFoo.\n"""
• Please add a docstring to testMultipleFactories.

Thanks so much.

[mwh]

Now with less Launchpad coding style.

[jml]

OK. This is approved to land.

[exarkun]

testBuildProtocol and testBuildProtocolRespectsProtocol are misnamed

[jml]

Oops, missed that.

Specifically, they should be test_buildProtocol and test_buildProtocolRespectsProtocol.

[mwh]

Like so?

[jml]

(In [24899]) Branching to 'ssh-factory-build-protocol-3443'

[jml]

(In [24901]) Make SSHFactory use self.protocol to construct protocol instances.

• Author: mwh
• Reviewer: jml
• Fixes #3443

Previously SSHFactory always instantiated an SSHServerTransport. This commit allows subclasses of SSHFactory to specify their own protocol -- usually a subclass of SSHServerTransport.