This change also makes it so that the test_rename_stream()
test exercises the code path. We need to subscribe the user
to the stream in order to generate events.
(imported from commit 77f965efbf5a766eb8de23486e303fa135b2e638)
Before this change, we were doing assertNotIn to verify that Cordelia
was not among our subscribers after calling /json/subscriptions/remove,
but we were then catching the AssertionError except for every case. We
really only want to bypass the assertion when the server had reported
an error.
(imported from commit 0bdaf23047b795721372251724228daf18677df5)
After extracting test_subs.py, I went back and tried to put as may
imports on a single line as possible without going over 80 chars.
I did this for the zerver.lib.actions section in tests.py too, where
some imports had been removed.
(imported from commit 6ec5bad0a5314aed597f3c55aaf31611598b84ff)
