py3: replace file() with open() in test-convert-mtn.t
While I was here, I added b'' prefixes to make sure we write things correctly in
bytes mode on Python 3.
Differential Revision: https://phab.mercurial-scm.org/D2111
py3: replace file() with open() in test-clone.t
While I was here, I made sure we write things correctly in bytes mode.
Differential Revision: https://phab.mercurial-scm.org/D2110