use python3.6 in debian:buster image

7 jobs for master in 6 minutes and 16 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Test
passed #15670
coverage

00:03:54

88.38%
passed #15666
isort

00:03:49

passed #15667
migrations

00:03:36

passed #15668
prospector

00:04:29

passed #15669
pylint

00:04:20

 
  Docs
passed #15671
docs

00:01:41

passed #15672
web

00:01:46