py3: replace file() with open() in test-mactext.t
file() is not present in Python 3.
This patch also adds a b'' prefix to make sure we write bytes in Python 3.
Differential Revision: https://phab.mercurial-scm.org/D2122
py3: replace file() with open() in test-mq-missingfiles.t
file() is not present in Python 3.
Differential Revision: https://phab.mercurial-scm.org/D2121