allow to run remove_client asynchronously through celery (#232)

4 jobs for master in 4 minutes and 22 seconds (queued for 9 seconds)
Status Job ID Name Coverage
  Test
passed #6033
lint
test:lint

00:01:17

passed #6034
docker
test:py3.6

00:02:40

48.0%
 
  Build
passed #6036
build
build:doc

00:01:41

passed #6035
build
build:py3

00:01:27