Dockerfile: stretch was using jessie-slim instead of stretch-slim

22 jobs for !25 with fix-debug-output-message in 26 minutes and 46 seconds (queued for 2 seconds)
detached
Status Job ID Name Coverage
  Build
passed #824
buster-slim

00:01:18

passed #834
jessie-slim

00:07:07

passed #835
stretch-slim

00:06:14

failed #822
jessie-slim

00:20:13

failed #823
stretch-slim

00:20:12

 
  Check
passed #840
compile

00:00:44

passed #841
lint

00:01:35

passed #842
pep8

00:01:13

failed #837
compile

00:00:29

failed #825
compile

00:00:44

failed #838
lint

00:00:31

failed #826
lint

00:00:45

failed #839
pep8

00:00:30

failed #827
pep8

00:00:44

 
  Unit Test
passed #830
buster-ut

00:01:51

passed #828
jessie-ut

00:01:42

passed #829
stretch-ut

00:01:42

 
  Lets Encrypt Staging
passed #833
buster-le-staging

00:06:09

88.0%
passed #844
jessie-le-staging

00:03:40

passed #843
stretch-le-staging

00:04:17

failed #831
jessie-le-staging

00:07:27

failed #832
stretch-le-staging

00:08:02