Displays task time left in minutes.

            `env`
                Runtime ``Environment`` instance.
            `args`
                Arguments object from arg parser.

def execute(self, env, args):
        """ Displays task time left in minutes.

            `env`
                Runtime ``Environment`` instance.
            `args`
                Arguments object from arg parser.
            """

        msg = u'Time Left: {0}m' if not args.short else '{0}'
        mins = max(0, self.total_duration - env.task.duration)
        env.io.write(msg.format(mins))