gistfile1.py

# -*- coding: utf-8 -*-
from celery.app import app_or_default

Task = app_or_default().create_task_cls

class TransactionalTask(Task):
    """A task whose execution is delayed until after the current transaction.
    """
    abstract = True

    @classmethod
    def original_apply_async(cls, *args, **kwargs):
        """Shortcut method to reach real implementation
        of celery.Task.apply_sync
        """
        return super(TransactionalTask, cls).apply_async(cls, *args, **kwargs)

    @classmethod
    def apply_async(cls, *args, **kwargs):
        _get_manager().append((cls, args, kwargs))

Can you remove @classmethods and try again?
Also, do you use it like below?

@app.task(base=TransactionalTask)