Fixing tests with tox 4.2.6

Remove basepython from testenv

Change-Id: I140fc14944522000a808fa6292baa5c726b2dccd

tox.ini

@@ -6,15 +6,15 @@ ignore_basepython_conflict = True
 
 [testenv]
 usedevelop = True
-basepython = python3
 install_command = pip install {opts} {packages}
 setenv =
    VIRTUAL_ENV={envdir}
 deps = -c{env:TOX_CONSTRAINTS_FILE:https://releases.openstack.org/constraints/upper/master}
        -r{toxinidir}/requirements.txt
        -r{toxinidir}/test-requirements.txt
+allowlist_externals = bash
 commands =
-  /bin/bash run_tests.sh -N --no-pep8 {posargs}
+  bash run_tests.sh -N --no-pep8 {posargs}
 
 [testenv:pep8]
 commands = flake8