Check that all po/pot files are valid

Perform minimal checks on po and pot files so that no broken files can
get imported.

Change-Id: I24e8543006830d0b0b1781bc2746b8eac700a971
Co-Authored-By: Clark Boylan <clark.boylan@gmail.com>
Related-Bug: #1299349

tox.ini

@@ -13,6 +13,7 @@ deps =
     -r{toxinidir}/requirements.txt
     -r{toxinidir}/test-requirements.txt
 commands = python setup.py test --slowest --testr-args="{posargs}"
+whitelist_externals = bash
 
 [testenv:integration]
 setenv =
@@ -30,6 +31,8 @@ downloadcache = ~/cache/pip
 commands =
     flake8 {posargs}
     {toxinidir}/tools/config/check_uptodate.sh
+    # Check that .po and .pot files are valid:
+    bash -c "find sahara -type f -regex '.*\.pot?' -print0|xargs -0 -n 1 msgfmt --check-format -o /dev/null"
 
 [testenv:venv]
 commands = {posargs}