module kombu.async not found

```
celeryworker_1 | Traceback (most recent call last):
celeryworker_1 | File "/usr/local/bin/celery", line 11, in
celeryworker_1 | sys.exit(main())
celeryworker_1 | File "/usr/local/lib/python3.6/site-packages/celery/__main__.py", line 12, in main
celeryworker_1 | maybe_patch_concurrency()
celeryworker_1 | File "/usr/local/lib/python3.6/site-packages/celery/__init__.py", line 146, in maybe_patch_concurrency
celeryworker_1 | concurrency.get_implementation(pool)
celeryworker_1 | File "/usr/local/lib/python3.6/site-packages/celery/concurrency/__init__.py", line 23, in get_implementation
celeryworker_1 | return symbol_by_name(cls, ALIASES)
celeryworker_1 | File "/usr/local/lib/python3.6/site-packages/kombu/utils/imports.py", line 56, in symbol_by_name
celeryworker_1 | module = imp(module_name, package=package, **kwargs)
celeryworker_1 | File "/usr/local/lib/python3.6/importlib/__init__.py", line 126, in import_module
celeryworker_1 | return _bootstrap._gcd_import(name[level:], package, level)
celeryworker_1 | File "", line 994, in _gcd_import
celeryworker_1 | File "", line 971, in _find_and_load
celeryworker_1 | File "", line 955, in _find_and_load_unlocked
celeryworker_1 | File "", line 665, in _load_unlocked
celeryworker_1 | File "", line 678, in exec_module
celeryworker_1 | File "", line 219, in _call_with_frames_removed
celeryworker_1 | File "/usr/local/lib/python3.6/site-packages/celery/concurrency/gevent.py", line 4, in
celeryworker_1 | from kombu.async import timer as _timer
celeryworker_1 | ModuleNotFoundError: No module named 'kombu.async'
```