[1.7.x] Fixed #22942 -- Noted that __init__.py files are required for management command detection.

Thanks Diego Cerdán for the suggestion.

Backport of 54546cee from master

docs/howto/custom-management-commands.txt

@@ -26,6 +26,10 @@ directory whose name doesn't begin with an underscore. For example::
         tests.py
         views.py
 
+On Python 2, be sure to include ``__init__.py`` files in both the
+``management`` and ``management/commands`` directories as done above or your
+command will not be detected.
+
 In this example, the ``closepoll`` command will be made available to any project
 that includes the ``polls`` application in :setting:`INSTALLED_APPS`.