Fixes for tox 4 on focal (ZOSCI system)

The zosci 3rd party CI has updated to using focal and tox 4 by default
for the runners, so these fixes ensure that the main development branch
continues to be compatible.

Change-Id: I95c5cf033ce077664c7a221d43b13dfe8d3ac504
Func-Test-Pr: https://github.com/openstack-charmers/zaza-openstack-tests/pull/1028

requirements.txt

@@ -10,7 +10,7 @@ setuptools<50.0.0  # https://github.com/pypa/setuptools/commit/04e3df22df840c6bb
 
 # Build requirements
 cffi==1.14.6; python_version < '3.6'  # cffi 1.15.0 drops support for py35.
-charm-tools==2.8.3; python_version < '3.10'
+charm-tools==2.8.5; python_version < '3.10'
 charm-tools; python_version >= '3.10'
 
 simplejson

tox.ini

@@ -33,7 +33,7 @@ allowlist_externals =
     charmcraft
     bash
     tox
-    rename.sh
+    {toxinidir}/rename.sh
 deps =
     -r{toxinidir}/requirements.txt