Fix charm for tox4 compatibility

Related-Bug: 2002788
Change-Id: If35466d52fe4f3301699a29ba14bc10d58adb345

osci.yaml

@@ -6,4 +6,4 @@
       needs_charm_build: true
       charm_build_name: swift-storage
       build_type: charmcraft
-      charmcraft_channel: 2.0/stable
+      charmcraft_channel: 2.1/stable

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 "$@"

test-requirements.txt

@@ -8,7 +8,6 @@
 #       all of its own requirements and if it doesn't, fix it there.
 #
 pyparsing<3.0.0  # aodhclient is pinned in zaza and needs pyparsing < 3.0.0, but cffi also needs it, so pin here.
-setuptools<50.0.0  # https://github.com/pypa/setuptools/commit/04e3df22df840c6bb244e9b27bc56750c44b7c85
 
 requests>=2.18.4
 
@@ -27,5 +26,4 @@ git+https://github.com/openstack-charmers/zaza-openstack-tests.git#egg=zaza.open
 git+https://opendev.org/openstack/tempest.git#egg=tempest
 
 croniter            # needed for charm-rabbitmq-server unit tests
-
-pyopenssl<=22.0.0
+psutil

tox.ini

@@ -9,47 +9,43 @@
 #       all of its own requirements and if it doesn't, fix it there.
 [tox]
 envlist = pep8,py3
-skipsdist = True
 # NOTE: Avoid build/test env pollution by not enabling sitepackages.
 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
 
 [testenv]
+# We use tox mainly for virtual environment management for test requirements
+# and do not install the charm code as a Python package into that environment.
+# Ref: https://tox.wiki/en/latest/config.html#skip_install
+skip_install = True
 setenv = VIRTUAL_ENV={envdir}
          PYTHONHASHSEED=0
          CHARM_DIR={envdir}
-install_command =
-  {toxinidir}/pip.sh 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]
 basepython = python3
 deps = -r{toxinidir}/build-requirements.txt
+# charmcraft clean is done to ensure that
+# `tox -e build` always performs a clean, repeatable build.
+# For faster rebuilds during development,
+# directly run `charmcraft -v pack && ./rename.sh`.
 commands =
     charmcraft clean
     charmcraft -v pack
     {toxinidir}/rename.sh
+    charmcraft clean
 
 [testenv:py310]
 basepython = python3.10