commands: Make sure parser errors get translated to correct error type.

mopidy/utils/command.py

@@ -7,6 +7,11 @@ class CommandError(Exception):
     pass
 
 
+class ArgumentParser(argparse.ArgumentParser):
+    def error(self, message):
+        raise CommandError(message)
+
+
 class Command(object):
     def __init__(self):
         self._children = collections.OrderedDict()
@@ -14,7 +19,7 @@ class Command(object):
 
     def _build(self):
         actions = []
-        parser = argparse.ArgumentParser(add_help=False)
+        parser = ArgumentParser(add_help=False)
 
         for args, kwargs in self._arguments:
             actions.append(parser.add_argument(*args, **kwargs))

tests/utils/command_test.py

@@ -103,6 +103,13 @@ class CommandParsingTest(unittest.TestCase):
         result = cmd.parse([])
         self.assertEqual(result.command, cmd)
 
+    def test_missing_positionals(self):
+        cmd = command.Command()
+        cmd.add_argument('foo')
+
+        with self.assertRaises(command.CommandError):
+            cmd.parse([])
+
 
 class UsageTest(unittest.TestCase):
     @mock.patch('sys.argv')