Cipher Checking

[Lukasa]

Setting ourselves to a really restricted cipher list as mandated by the specification breaks on Ubuntu 12.04 because Ubuntu are fucking terrible. I've spent all of yesterday trying to fix this and come up blank, so I'm going to take a new option:

1. Add a HTTP20Connection property called 'strict TLS' (or similar), defaulting to True.
2. In HTTP20Connection.connect(), if that parameter is True, check the selected cipher.

Unfortunately, I can't do this yet because PyOpenSSL doesn't support checking the used cipher until 0.15, which isn't out yet. Sigh.

[Lukasa]

I think this approach is OK because client cipher suites aren't authoritative anyway, the server makes the choice, so all I can really do is ensure that the server made a good choice.

[Lukasa]

I'm unblocking this because I think PyOpenSSL is basically dead now.