Returns command class from the registry for a given ``cmd``.

        :param cmd: command to run (key at the registry)

def get_command_class(self, cmd):
        """
        Returns command class from the registry for a given ``cmd``.

        :param cmd: command to run (key at the registry)
        """
        try:
            cmdpath = self.registry[cmd]
        except KeyError:
            raise CommandError("No such command %r" % cmd)
        if isinstance(cmdpath, basestring):
            Command = import_class(cmdpath)
        else:
            Command = cmdpath
        return Command