Fix py38-django31 test and add codecov badge

8 jobs for master in 3 minutes and 42 seconds (queued for 1 second)
latest
Status Job ID Name Coverage
  Pre Commit
passed #1186582657
pre-commit-check

00:00:43

 
  Test
passed #1186582662
test-36-django22

00:01:36

91.0%
passed #1186582663
test-36-django31

00:01:38

91.0%
passed #1186582665
test-37-django22

00:01:33

91.0%
passed #1186582666
test-37-django31

00:01:20

91.0%
passed #1186582669
test-38-django22

00:01:20

91.0%
passed #1186582672
test-38-django31

00:01:19

91.0%
passed #1186582660
test-docs

00:01:33