py3: open patches.queue in binary mode
And switch to using the context manager form of open() while we're
here.
Differential Revision: https://phab.mercurial-scm.org/D2153
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https://www.mercurial-scm.org/wiki/ContributingChanges
If you just want a checklist to follow, you can go straight to
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273ce12ad8f1` will report some style violations on a very old commit).