remove scary error message in tox

Found an interesting cantrip in the devstack tox.ini that gets rid of
the scary can't find bash error message at the beginning of test
runs. Reducing non error looking error things make it easier to see
real errors.

Change-Id: I4e1b826626063bf8d5a15531f5768f9ce0eea6a5
Merge "remove scary error message in tox"