py3: whitelist another nine passing tests
I now see 347 tests passing[0] and 336 failing, so we're past halfway
there. Hooray!
0: A few tests appear to regress in small ways (doctest output
changes, for example) on Python 3.7.0a1, which is what I'm now
using to test. That said, I'm pleased to report no major regressions.
Differential Revision: https://phab.mercurial-scm.org/D2439