Small fixes in doc + missing app_gui.stop on error

pytest_gui_status/status_gui/gui_backend.py

@@ -59,7 +59,8 @@ class Controller(htmlPy.Object):
         hash_dir_name = redis_db.hget("directories_to_hash", dir_name)
 
         if hash_dir_name is None:
-            raise Exception("dir_name = {dir_name} not found in redis db".format(
+            self.app_gui.stop()
+            raise redis.exceptions.ConnectionError("dir_name = {dir_name} not found in redis db".format(
                 dir_name=dir_name))
 
         dict_state = {}

tests/test_plugin/test_plugin.py

@@ -43,6 +43,9 @@ def reload_2_3(module_name):
     reload that works in all versions of Python.
     Uses builtin reload in py2, imp.reload for <=py3.3,
     importlib.reload for >=3.4
+
+    The module six has similar functionalities,
+    but would be too huge a dependency for this simple case.
     '''
 
     from sys import version_info