help, makeapi: do not use hardcoded plugin package name

Iterate over all plugin packages defined in the API to find the given
topic module. The last module found has priority.

This will allow topics to be defined in client-side plugins.

https://fedorahosted.org/freeipa/ticket/4739

Reviewed-By: David Kupka <dkupka@redhat.com>

ipalib/cli.py

@@ -691,17 +691,26 @@ class help(frontend.Local):
 
     topic = None
 
-    _PLUGIN_BASE_MODULE = 'ipalib.plugins'
-
     def _get_topic(self, topic):
-        module_name = '%s.%s' % (self._PLUGIN_BASE_MODULE, topic)
-        try:
-            module = sys.modules[module_name]
-        except KeyError:
-            module = importlib.import_module(module_name)
+        doc = u''
+        parent_topic = None
 
-        doc = unicode(module.__doc__ or '').strip()
-        parent_topic = getattr(module, 'topic', None)
+        for package in self.api.packages:
+            module_name = '%s.%s' % (package.__name__, topic)
+            try:
+                module = sys.modules[module_name]
+            except KeyError:
+                try:
+                    module = importlib.import_module(module_name)
+                except ImportError:
+                    continue
+
+            if module.__doc__ is not None:
+                doc = unicode(module.__doc__ or '').strip()
+            try:
+                parent_topic = module.topic
+            except AttributeError:
+                pass
 
         return doc, parent_topic
 
@@ -763,7 +772,6 @@ class help(frontend.Local):
             outfile = sys.stdout
         writer = self._writer(outfile)
         name = from_cli(key)
-        mod_name = '%s.%s' % (self._PLUGIN_BASE_MODULE, name)
         if key is None:
             self.api.parser.print_help(outfile)
             return
@@ -777,7 +785,8 @@ class help(frontend.Local):
             if cmd.NO_CLI:
                 raise HelpError(topic=name)
             self.Backend.cli.build_parser(cmd).print_help(outfile)
-        elif mod_name in sys.modules:
+        elif any(name in t[2] for t in self._topics.values()
+                 if type(t[2]) is dict):
             self.print_commands(name, outfile)
         elif name == "commands":
             mcl = max(len(s) for s in (self.Command))
@@ -827,8 +836,7 @@ class help(frontend.Local):
                     commands = self._topics[t][2][topic][2]
                     break
 
-            m = '%s.%s' % (self._PLUGIN_BASE_MODULE, topic)
-            doc = (unicode(_(sys.modules[m].__doc__)) or '').strip()
+            doc, _topic = self._get_topic(topic)
 
             if topic not in self.Command and len(commands) == 0:
                 raise HelpError(topic=topic)