Issue error message at plugin load if a command has no docstring.

src/commands.py

@@ -1039,9 +1039,10 @@ class Spec(object):
         return state
 
 def _wrap(f, specList=[], name=None, **kw):
-    assert hasattr(f, '__doc__')
-    f = internationalizeDocstring(f)
     name = name or f.func_name
+    assert hasattr(f, '__doc__') and f.__doc__, \
+                'Command %r has no docstring.' % name
+    f = internationalizeDocstring(f)
     spec = Spec(specList, **kw)
     def newf(self, irc, msg, args, **kwargs):
         state = spec(irc, msg, args, stateAttrs={'cb': self, 'log': self.log})