A bunch of readability suggestions for t.c.test.test_session

New submission from jkk <None>:

Those are things I found confusing when going trough r27376:
 * StubAvatar? doesn't implement ISession, but docstring says it does.
 * StubSessionForStubAvatar?.execCommand docstring doesn't describe method's code correctly.
 * MockProcessProtocol? isn't used anywhere, should it be?
 * SessionInterfaceTestCase?.assertSessionIsStubSession's docstring mentions StubSessionForStubOldAvatar? which doesn't exists.
 * StubAvatar? and StubTransport? aren't new style classes

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Type     : task
Component: conch
Keywords : 
Priority : normal
Nosy     : 
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http://twistedmatrix.com/trac/ticket/4057