hg: be more strict about which kinds of revision lookup we want from hg Comply with https://www.mercurial-scm.org/repo/hg/file/4.6/mercurial/context.py#l380 to support recent Mercurial versions.

babel >= 0.9.6, < 2.4
waitress >= 0.8.8, < 1.0
pytest ~= 3.0, >= 3.3.0
pytest-runner
pytest-sugar>=0.7.0
pytest-benchmark
pytest-localserver
mock
sphinx
webtest < 3