issue #579. @@tx_isolation is deprecated since MYSQL 5.7.20, add mysq… (#581)
issue #579. @@tx_isolation is deprecated since MYSQL 5.7.20, add mysq… (#581)

* issue #579. @@tx_isolation is deprecated since MYSQL 5.7.20, add mysql version check

* issue #579. @@tx_isolation is deprecated since MYSQL 5.7.20, add mysql version check & add decoding for python3

celery/django-celery,celery/django-celery,celery/django-celery