tests: Avoid pytrace=False for now.

Using pytest.fail with pytrace=False hides the quteprocess output, which makes
it a lot harder to debug stuff.

This is because TestReport.longrepr is suddenly a string and we can't add infos
to it - see pytest-dev/pytest#1316

tests/integration/quteprocess.py

@@ -229,7 +229,9 @@ def after_test(self):
         if bad_msgs:
             text = 'Logged unexpected errors:\n\n' + '\n'.join(
                 str(e) for e in bad_msgs)
-            pytest.fail(text, pytrace=False)
+            # We'd like to use pytrace=False here but don't as a WORKAROUND
+            # for https://github.com/pytest-dev/pytest/issues/1316
+            pytest.fail(text)
 
     def send_cmd(self, command, count=None):
         """Send a command to the running qutebrowser instance."""