Revert "Check for python warnings as well"

This reverts commit 2c5bab4b.

.travis.yml

@@ -31,7 +31,7 @@ script:
   - ./manage.py validate --settings weblate.settings_test
   - ./manage.py syncdb --noinput --settings weblate.settings_test
   - ./manage.py migrate --settings weblate.settings_test --traceback
-  - python -W error `which coverage` run --source=. ./manage.py test --settings weblate.settings_test $TRAVIS_RUN_TESTS 
+  - coverage run --source=. ./manage.py test --settings weblate.settings_test $TRAVIS_RUN_TESTS 
   - pep8 --exclude migrations weblate
   - pylint --reports=n --rcfile=pylint.rc weblate
 after_success: