Code review comment for lp:~gz/bzr/test_ssh_client_medium_eintr__read_bytes

For background, see this thread (and particularly the three changesets linked ffrom the initial post):
<https://lists.ubuntu.com/archives/bazaar/2010q1/066869.html>

There seemed to be some doubt about exactly how harmful the current code attempting to handle EINTR is, despite my best attempts to explain it, so here's a test that demonstrates a couple of the failure states. It uses a reading method, but these problems apply equally to those that write, it's just harder to get them to block where you want reliably enough to make an automated test.

As an aside, testtools doesn't seem to do anything sensible with TestCase.knownFailure (and the TestCase.expectFailure isn't much better).