PR#645: don't fail on CLI plugins without docstrings

Merges #645
https://pagure.io/koji/pull-request/645

Fixes: #644
https://pagure.io/koji/issue/644
CLI fails on plugins without docstrings

cli/koji

@@ -275,7 +275,7 @@ def list_commands(categories_chosen=None):
     for category in categories_chosen:
         print(_("\n%s:" % categories[category]))
         for alias,handler in handlers:
-            desc = handler.__doc__
+            desc = handler.__doc__ or ''
             if desc.startswith('[%s] ' % category):
                 desc = desc[len('[%s] ' % category):]
             elif category != 'misc' or desc.startswith('['):

docs/source/writing_a_plugin.rst

@@ -206,6 +206,7 @@ Most simple command would look like this:
 
     @export_cli
     def anon_handle_echo(options, session, args):
+        "[info] Print arguments"
         usage = _("usage: %prog echo <message>")
         parser = OptionParser(usage=usage)
         (opts, args) = parser.parse_args(args)