encode filenames as bytes to handle all locale setups

encode filenames as bytes to handle all locale setups

This was failing on environments that did not have any LANG or LC_* locale
variables set.  This is a valid setup, and is common in headless setups, so
it needs to be handled.

This also adds a new pass of the test suite without the locale env vars set
so that this situation is also tests on gitlab-ci, not only gpjenkins.

The error this caused was:
UnicodeEncodeError: 'ascii' codec can't encode characters in position 6-18: ordinal not in range(128)