Replace appdirs usage with platformdirs

The appdirs library has been abandoned for several years now, and a
fork named platformdirs is the recommended alternative. It's almost
a drop-in replacement, except the module and convenience class name
have changed. Adjust the internal variable name we're using for the
expansion to match as well, for all those consistent hobgoblins.

Add it with a >=3 lower bound because that introduces a breaking
change of the default configuration location for macOS users.
Include a release note about that too.

Depends-On: https://review.opendev.org/886642
Change-Id: I4c2b60ca0da29da1f605b4c0b5e77f8e1071a19c

openstack/config/loader.py

@@ -23,9 +23,9 @@ import re
 import sys
 import warnings
 
-import appdirs
 from keystoneauth1 import adapter
 from keystoneauth1 import loading
+import platformdirs
 import yaml
 
 from openstack import _log
@@ -36,9 +36,11 @@ from openstack.config import vendors
 from openstack import exceptions
 from openstack import warnings as os_warnings
 
-APPDIRS = appdirs.AppDirs('openstack', 'OpenStack', multipath='/etc')
-CONFIG_HOME = APPDIRS.user_config_dir
-CACHE_PATH = APPDIRS.user_cache_dir
+PLATFORMDIRS = platformdirs.PlatformDirs(
+    'openstack', 'OpenStack', multipath='/etc'
+)
+CONFIG_HOME = PLATFORMDIRS.user_config_dir
+CACHE_PATH = PLATFORMDIRS.user_cache_dir
 
 # snaps do set $HOME to something like
 # /home/$USER/snap/openstackclients/$SNAP_VERSION
@@ -55,7 +57,7 @@ else:
     )
 UNIX_SITE_CONFIG_HOME = '/etc/openstack'
 
-SITE_CONFIG_HOME = APPDIRS.site_config_dir
+SITE_CONFIG_HOME = PLATFORMDIRS.site_config_dir
 
 CONFIG_SEARCH_PATH = [
     os.getcwd(),

releasenotes/notes/replace-appdirs-with-platformdirs-d3f5bcbe726b7829.yaml

@@ -0,0 +1,8 @@
+---
+upgrade:
+  - |
+    The ``appdirs`` dependency is replaced by a requirement for
+    ``platformdirs`` 3.0.0 or later. Users on macOS may need to move
+    configuration files to ``*/Library/Application Support``. See its release
+    notes for further details:
+    https://platformdirs.readthedocs.io/en/latest/changelog.html#platformdirs-3-0-0-2023-02-06

requirements.txt

@@ -3,7 +3,7 @@
 # process, which may cause wedges in the gate later.
 pbr!=2.1.0,>=2.0.0 # Apache-2.0
 PyYAML>=3.13 # MIT
-appdirs>=1.3.0 # MIT License
+platformdirs>=3 # MIT License
 requestsexceptions>=1.2.0 # Apache-2.0
 jsonpatch!=1.20,>=1.16 # BSD
 os-service-types>=1.7.0 # Apache-2.0