test pylint in buster

.gitlab-ci.yml

 linter:
-  image: debian:stretch
+  image: debian:busterh
   stage: test
   script:
   - apt update
   - apt install -y python3
   - python3 -V
   - uname -a
-  - apt install -y sqlite3 locales-all git python3-flask python3-ldap3 python3-requests python3-lxml python3-icalendar python3-mysql.connector python3-requests python3-coverage pylint3
+  - apt install -y sqlite3 locales-all git python3-flask python3-ldap3 python3-requests python3-lxml python3-icalendar python3-requests python3-coverage pylint3
   - pylint3 --indent-string='\t' --indent-after-paren=1 --max-line-length=160 --disable=missing-docstring,unused-wildcard-import --output-format=text *.py | tee pylint.txt
   artifacts:
       paths: