why did those tests fail???

.travis.yml

@@ -16,7 +16,7 @@ install:
 - chromium-browser --version
 - sudo service brozzler-worker restart
 script:
-- DISPLAY=:1 py.test -v tests
+- DISPLAY=:1 py.test --tb=native -v tests
 after_failure:
 - chromium-browser --version
 - sudo cat /var/log/upstart/warcprox.log

tests/test_cli.py

@@ -53,9 +53,9 @@ def test_run_command(capsys, cmd):
     proc = subprocess.Popen(
         [cmd, '--version'], stdout=subprocess.PIPE, stderr=subprocess.PIPE)
     out, err = proc.communicate()
+    assert err == b''
     assert out == ('brozzler %s - %s\n' % (
         brozzler.__version__, cmd)).encode('ascii')
-    assert err == b''
 
 def test_rethinkdb_up():
     '''Check that rethinkdb is up and running.'''