print usage on invalid command-line arguments

IPython/config/application.py

@@ -24,7 +24,7 b' import sys'
 
 from IPython.config.configurable import SingletonConfigurable
 from IPython.config.loader import (
-    KeyValueConfigLoader, PyFileConfigLoader, Config
+    KeyValueConfigLoader, PyFileConfigLoader, Config, ArgumentError
 )
 
 from IPython.utils.traitlets import (
@@ -175,8 +175,10 b' class Application(SingletonConfigurable):'
         lines.append('')
         
         classdict = {}
-        for c in self.classes:
-            classdict[c.__name__] = c
+        for cls in self.classes:
+            # include all parents in available names
+            for c in cls.mro():
+                classdict[c.__name__] = c
         
         for alias, longname in self.aliases.iteritems():
             classname, traitname = longname.split('.',1)
@@ -212,7 +214,7 b' class Application(SingletonConfigurable):'
         
         lines = ["Subcommands"]
         lines.append('-'*len(lines[0]))
-        for subc, cls,help in self.subcommands:
+        for subc, (cls,help) in self.subcommands.iteritems():
             lines.append("%s : %s"%(subc, cls))
             if help:
                 lines.append(indent(help, flatten=True))
@@ -267,14 +269,14 b' class Application(SingletonConfigurable):'
             self.print_description()
             self.print_subcommands()
             self.exit(0)
-        subapp = self.subcommands.get(subc, None)
+        subapp,help = self.subcommands.get(subc, (None,None))
         if subapp is None:
             self.print_description()
             print "No such subcommand: %r"%subc
             print
             self.print_subcommands()
             self.exit(1)
-            
+        
         if isinstance(subapp, basestring):
             subapp = import_item(subapp)
         
@@ -308,7 +310,13 b' class Application(SingletonConfigurable):'
         
         loader = KeyValueConfigLoader(argv=argv, aliases=self.aliases,
                                         flags=self.flags)
-        config = loader.load_config()
+        try:
+            config = loader.load_config()
+        except ArgumentError as e:
+            self.log.fatal(str(e))
+            self.print_description()
+            self.print_help()
+            self.exit(1)
         self.update_config(config)
 
     def load_config_file(self, filename, path=None):

IPython/config/loader.py

@@ -36,6 +36,9 b' class ConfigError(Exception):'
 class ConfigLoaderError(ConfigError):
     pass
 
+class ArgumentError(ConfigLoaderError):
+    pass
+
 #-----------------------------------------------------------------------------
 # Argparse fix
 #-----------------------------------------------------------------------------
@@ -403,14 +406,14 b' class KeyValueConfigLoader(CommandLineConfigLoader):'
                 m = item[2:]
                 cfg,_ = flags.get(m, (None,None))
                 if cfg is None:
-                    raise ValueError("Unrecognized flag: %r"%item)
+                    raise ArgumentError("Unrecognized flag: %r"%item)
                 elif isinstance(cfg, (dict, Config)):
                     # update self.config with Config:
                     self.config.update(cfg)
                 else:
                     raise ValueError("Invalid flag: %r"%flag)
             else:
-                raise ValueError("Invalid argument: %r"%item)
+                raise ArgumentError("Invalid argument: %r"%item)
         return self.config
 
 class ArgParseConfigLoader(CommandLineConfigLoader):