docs: def execute(self, env, args):
          """ Edits task configuration.
  
              `env`
                  Runtime ``Environment`` instance.
              `args`
                  Arguments object from arg parser.
              """
  
          task_name = args.task_name
  
          if not env.task.exists(task_name):
              raise errors.TaskNotFound(task_name)
  
          if env.task.active and task_name == env.task.name:
              raise errors.ActiveTask
  
          # open in task config in editor
          task_config = env.task.get_config_path(task_name)
  
          if not _edit_task_config(env, task_config, confirm=True):
              raise errors.FocusError(u'Could not open task config: {0}'
                                      .format(task_config))