Adds to Melange a tags framework based on taggable-mixin. The taggable-mixin allowed only tag per Datastore model. This is extended framework allows any arbitrary number of tags per Datastore model. Also, now one can define different models for different Tag types which are all inherited from the base Tag model provided by taggable-mixin. The GHOPTask model makes use of 2 tags per model, one for difficulty and the other for task_type, both using the tags framework. Reviewed by: Paweł Sołyga

from django.core.management.base import BaseCommand, CommandError

class ArgsCommand(BaseCommand):
    """
    Command class for commands that take multiple arguments.
    """
    args = '<arg arg ...>'

    def handle(self, *args, **options):
        if not args:
            raise CommandError('Must provide the following arguments: %s' % self.args)
        return self.handle_args(*args, **options)

    def handle_args(self, *args, **options):
        raise NotImplementedError()