Add kombu to base (celery) dependencies
Using latest version 4.4.0, previous suitable 4.3.0
also had bug: kombu/issues#1006
@@ -11,6 +11,7 @@ whitenoise==4.1.2 # https://github.com/evansd/whitenoise
redis>=3.2.0 # https://github.com/antirez/redis
{%- if cookiecutter.use_celery == "y" %}
celery==4.2.1 # pyup: < 5.0 # https://github.com/celery/celery
+kombu==4.4.0 # https://github.com/celery/kombu
{%- if cookiecutter.use_docker == 'y' %}
flower==0.9.2 # https://github.com/mher/flower
{%- endif %}
