Update allowlist_externals with full path to commands

Pin flake8 < 6 to avoid plugin incompatibilities.

Pattern match any status message from mysql-k8s.

Change-Id: I5464a0722ddf8693b88d406aa1beab1374731d65

charms/keystone-k8s/tests/tests.yaml

@@ -37,4 +37,4 @@ target_deploy_status:
     workload-status-message-regex: '^$'
   mysql:
     workload-status: active
-    workload-status-message-regex: '^$'
+    workload-status-message-regex: '^.*$'

charms/keystone-k8s/tox.ini

@@ -30,8 +30,8 @@ commands = stestr run --slowest {posargs}
 allowlist_externals =
   git
   charmcraft
-  fetch-libs.sh
-  rename.sh
+  {toxinidir}/fetch-libs.sh
+  {toxinidir}/rename.sh
 deps =
   -r{toxinidir}/test-requirements.txt
 
@@ -98,8 +98,7 @@ commands = {[testenv:lint]commands}
 description = Check code against coding style standards
 deps =
     black
-    # flake8==4.0.1 # Pin version until https://github.com/csachs/pyproject-flake8/pull/14 is merged
-    flake8
+    flake8<6
     flake8-docstrings
     flake8-copyright
     flake8-builtins