ci: install tox in py38 job

A better approach would be to backport python definition in several jobs inside gitlab-ci-templates
13 jobs for !49 with topic/default/tox-in-py38 in 1 minute and 11 seconds (queued for 39 seconds)
latest detached
Status Name Job ID Coverage
  Lint
failed black #487549
lint black

00:00:36

passed check-manifest #487552
lint check-manifest

00:00:29

passed flake8 #487550
lint flake8

00:00:41

failed mypy #487551
lint mypy allowed to fail

00:00:53

passed yamllint #487553
lint yamllint

00:00:33

 
  Tests
failed py3 #487554
tests py3

00:00:46

passed py38 #487555
tests py3

00:00:56

 
  After Tests
skipped trigger-cubicweb-pipeline
skipped trigger-logilab-constraint-pipeline
skipped trigger-logilab-database-pipeline
skipped trigger-logilab-mtconverter-pipeline
skipped trigger-rql-pipeline
skipped trigger-yams-pipeline
 
Name Stage Failure
failed
py3 Tests
Uploading artifacts for failed job
Uploading artifacts...
py3-deprecated-warnings.json: found 1 matching files and directories

Uploading artifacts as "archive" to coordinator... ok
id=487554 responseStatus=201 Created token=Z_xsz-sY
Uploading artifacts...
report.xml: found 1 matching files and directories

Uploading artifacts as "junit" to coordinator... ok
id=487554 responseStatus=201 Created token=Z_xsz-sY
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1
failed
mypy Lint
logilab/common/optik_ext.py:364: note: See https://mypy.readthedocs.io/en/stable/common_issues.html#incompatible-overrides
logilab/common/optik_ext.py:370: error: Argument 1 to "format_option_strings" of "HelpFormatter" has incompatible type "OptionParser"; expected "Option"
logilab/common/registry.py:560: error: Argument 3 to "getattr" has incompatible type "int"; expected "str"
Found 7 errors in 4 files (checked 41 source files)
ERROR: InvocationError for command /builds/open-source/logilab-common/.tox/mypy/bin/mypy --ignore-missing-imports logilab (exited with code 1)
___________________________________ summary ____________________________________
ERROR: mypy: commands failed
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1
failed
black Lint
would reformat logilab/common/debugger.py
would reformat test/test_textutils.py
Oh no! 💥 💔 💥
3 files would be reformatted, 81 files would be left unchanged.
ERROR: InvocationError for command /builds/open-source/logilab-common/.tox/black/bin/black --check . (exited with code 1)
___________________________________ summary ____________________________________
ERROR: black: commands failed
Cleaning up file based variables
ERROR: Job failed: command terminated with exit code 1