Remove unneeded msgfmt test

The infra scripts run msgfmt since some time, no need to run it here as
well.

This fixes the pep8 failure in https://review.openstack.org/#/c/493290/
since that change removes the remaining po files and now the find fails
since there is no po file anymore.

Change-Id: I6a8b99a9d63e421f4a6eae6f0aab6d0955f7916b

tox.ini

@@ -26,9 +26,6 @@ sitepackages = True
 basepython = python2.7
 commands =
     flake8
-    # Check that .po and .pot files are valid:
-    bash -c "find trove -type f -regex '.*\.pot?' -print0 | \
-             xargs -0 -n 1 msgfmt --check-format -o /dev/null"
 
 [testenv:py27]
 commands = {[testenv]commands}