Reformat source files with black (#3100)

The latest black version changed a few formatting rules, causing the lint
stage to fail. Changes in this commit make sure black is happy again.

src/molecule/command/idempotence.py

@@ -87,7 +87,7 @@ def execute(self):
             LOG.info(msg)
         else:
             msg = (
-                "Idempotence test failed because of the following tasks:\n" u"{}"
+                "Idempotence test failed because of the following tasks:\n{}"
             ).format("\n".join(self._non_idempotent_tasks(output)))
             util.sysexit_with_message(msg)
 
@@ -132,7 +132,7 @@ def _non_idempotent_tasks(self, output):
             elif line.startswith("changed"):
                 host_name = re.search(r"\[(.*)\]", line).groups()[0]
                 task_name = re.search(r"\[(.*)\]", task_line).groups()[0]
-                res.append(u"* [{}] => {}".format(host_name, task_name))
+                res.append("* [{}] => {}".format(host_name, task_name))
 
         return res