Resolve occasionally failing testcases

* instruct pytest to ignore the .git folder for test discovery (faster startup on slow disks)
* change test comparing two runs of ``ls -l /bin`` to something more reliable, ``uname -m -n ...``. This test occasionally fails on OSX, the git commit message demonstrates -- extra newlines appear on occasion?!
* create (and teardown) a temporary file for use with bash as argument ``--rcfile`` containing a static value for ``PS1``. My own prompt happens to be a bit jokey, reading ``C:\Users\docker\Code\pexpect>`` which causes this test to fail unless it is forced.  This is also failing on a SunOS build slave I'm working on, though I'm not entirely sure why, as the prompt reads ``-bash-4.1$ ``