Unpin tox version

This unpinning is meant to solve the issues with tox 4.x breaking
all the virtualenv dependencies.

Change-Id: Ifc3381b2f2e4e41ebf6676080bf1831baffb0d42

osci.yaml

@@ -20,4 +20,4 @@
       - charm-build
       - tox-py38
     vars:
-      tox_extra_args: install:local-focal-yoga
+      tox_extra_args: '-- install:local-focal-yoga'

pip.sh

@@ -1,18 +0,0 @@
-#!/usr/bin/env bash
-#
-# This file is managed centrally by release-tools and should not be modified
-# within individual charm repos.  See the 'global' dir contents for available
-# choices of tox.ini for OpenStack Charms:
-#     https://github.com/openstack-charmers/release-tools
-#
-# setuptools 58.0 dropped the support for use_2to3=true which is needed to
-# install blessings (an indirect dependency of charm-tools).
-#
-# More details on the beahvior of tox and virtualenv creation can be found at
-# https://github.com/tox-dev/tox/issues/448
-#
-# This script is wrapper to force the use of the pinned versions early in the
-# process when the virtualenv was created and upgraded before installing the
-# depedencies declared in the target.
-pip install 'pip<20.3' 'setuptools<50.0.0'
-pip "$@"

requirements.txt

@@ -11,4 +11,4 @@ git+https://opendev.org/openstack/charm-ops-openstack#egg=ops_openstack
 git+https://opendev.org/openstack/charm-ops-interface-tls-certificates#egg=interface_tls_certificates
 git+https://github.com/openstack-charmers/ops-interface-ceph-iscsi-admin-access#egg=interface_ceph_iscsi_admin_access
 git+https://github.com/openstack-charmers/ops-interface-openstack-loadbalancer#egg=interface_openstack_loadbalancer
-git+https://github.com/juju/charm-helpers#egg=charm-helpers
+git+https://github.com/juju/charm-helpers#egg=charmhelpers

tox.ini

@@ -14,18 +14,6 @@ skipsdist = True
 sitepackages = False
 # NOTE: Avoid false positives by not skipping missing interpreters.
 skip_missing_interpreters = False
-# NOTES:
-# * We avoid the new dependency resolver by pinning pip < 20.3, see
-#   https://github.com/pypa/pip/issues/9187
-# * Pinning dependencies requires tox >= 3.2.0, see
-#   https://tox.readthedocs.io/en/latest/config.html#conf-requires
-# * It is also necessary to pin virtualenv as a newer virtualenv would still
-#   lead to fetching the latest pip in the func* tox targets, see
-#   https://stackoverflow.com/a/38133283
-requires =
-  pip < 20.3
-  virtualenv < 20.0
-  setuptools < 50.0.0
 
 # NOTE: https://wiki.canonical.com/engineering/OpenStack/InstallLatestToxOnOsci
 minversion = 3.18.0
@@ -35,12 +23,17 @@ setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
          CHARM_DIR={envdir}
 install_command =
-  {toxinidir}/pip.sh install {opts} {packages}
+    pip install {opts} {packages}
 commands = stestr run --slowest {posargs}
 allowlist_externals =
     charmcraft
     rename.sh
-passenv = HOME TERM CS_* OS_* TEST_*
+passenv =
+    HOME
+    TERM
+    CS_*
+    OS_*
+    TEST_*
 deps = -r{toxinidir}/test-requirements.txt
 
 [testenv:build]