ext/backend: Use utils.command directly.

Commands don't "belong" to backends or frontends so just leave it at an ext
level and start using mopidy.utils.command directly.

mopidy/backends/base.py

@@ -2,8 +2,6 @@ from __future__ import unicode_literals
 
 import copy
 
-from mopidy.utils import command
-
 
 class Backend(object):
     #: Actor proxy to an instance of :class:`mopidy.audio.Audio`.
@@ -281,42 +279,3 @@ class BasePlaylistsProvider(object):
         *MUST be implemented by subclass.*
         """
         raise NotImplementedError
-
-
-# Re-exporting from this location for backends.
-class Command(command.Command):
-    pass
-
-
-# TODO: remove
-class BaseSubCommandProvider(object):
-    """Sub-classes may optionally add arguments to the passed in parser.
-
-    :param parser: parser you may add arguments to
-    :type parser: :class:`argparse.ArgumentParser`
-    """
-
-    name = None
-    """What the sub-command should be called. Will be run as ``mopidy NAME``.
-
-    Will be converted to :type:`bytes` and should be limited to ASCII
-    characters.  Example: ``scan``
-    """
-
-    help = None
-    """Optional help text for the sub-command, will be displayed in help."""
-
-    def __init__(self, parser):
-        pass
-
-    def run(self, args, config, extensions):
-        """Run the sub-command implemented by this provider.
-
-        *MUST be implemented by subclass.*
-
-        :param args: the argments object from argparse
-        :param config: read-only version of the mopidy config
-        :param extensions: list of enabled extensions
-        :returns: integer exit value for the process
-        """
-        raise NotImplementedError

mopidy/backends/local/command.py

@@ -6,21 +6,20 @@ import time
 
 from mopidy import exceptions
 from mopidy.audio import scan
-from mopidy.backends import base
-from mopidy.utils import path
+from mopidy.utils import command, path
 
 from . import translator
 
 logger = logging.getLogger('mopidy.backends.local.scan')
 
 
-class LocalCommand(base.Command):
+class LocalCommand(command.Command):
     def __init__(self):
         super(LocalCommand, self).__init__()
         self.add_child('scan', ScanCommand())
 
 
-class ScanCommand(base.Command):
+class ScanCommand(command.Command):
     """Scan local media files"""
 
     def run(self, args, config, extensions):

mopidy/ext.py

@@ -87,15 +87,12 @@ class Extension(object):
         """
         return []
 
-    def get_sub_commads(self):
-        # TODO: remove
-        return []
-
     def get_command(self):
         """Command to expose to command line users running mopidy.
 
         :returns:
-          :class:`~mopidy.backends.base.Command` instance
+          Instance of a :class:`~mopidy.utils.command.Command` class
+          or sub-class.
         """
         pass