ports-mgmt/packagekit: unbreak build with python != 3.9 (+)

* Declare build and run dependency on python
* Fix hardcoded python version in plist by %%PYTHON_SITELIBDIR%% macro
* Pet stage-qa
* While here, pass maintainership gnome->desktop

With hat:	desktop

Sponsored by:	Serenity Cybersecurity, LLC

ports-mgmt/packagekit/Makefile

 PORTNAME=	PackageKit
 PORTVERSION=	1.2.6
-PORTREVISION=	1
+PORTREVISION=	2
 CATEGORIES=	ports-mgmt sysutils
 MASTER_SITES=	https://www.freedesktop.org/software/PackageKit/releases/
 
-MAINTAINER=	gnome@FreeBSD.org
+MAINTAINER=	desktop@FreeBSD.org
 COMMENT=	DBUS packaging abstraction layer
 WWW=		https://www.freedesktop.org/software/PackageKit/
 
@@ -19,7 +19,7 @@ LIB_DEPENDS=	libfontconfig.so:x11-fonts/fontconfig \
 RUN_DEPENDS=	console-kit-daemon:sysutils/consolekit2
 
 USES=		cpe desktop-file-utils gettext gnome meson pkgconfig \
-		shared-mime-info shebangfix sqlite:3 tar:xz
+		python shared-mime-info shebangfix sqlite:3 tar:xz
 
 USE_GNOME=	gtk30 glib20 intltool introspection
 USE_LDCONFIG=	yes

ports-mgmt/packagekit/pkg-plist

@@ -54,13 +54,13 @@ lib/packagekit-backend/libpk_backend_test_nop.so
 lib/packagekit-backend/libpk_backend_test_spawn.so
 lib/packagekit-backend/libpk_backend_test_succeed.so
 lib/packagekit-backend/libpk_backend_test_thread.so
-lib/python3.9/site-packages/packagekit/__init__.py
-lib/python3.9/site-packages/packagekit/backend.py
-lib/python3.9/site-packages/packagekit/enums.py
-lib/python3.9/site-packages/packagekit/filter.py
-lib/python3.9/site-packages/packagekit/misc.py
-lib/python3.9/site-packages/packagekit/package.py
-lib/python3.9/site-packages/packagekit/progress.py
+%%PYTHON_SITELIBDIR%%/packagekit/__init__.py
+%%PYTHON_SITELIBDIR%%/packagekit/backend.py
+%%PYTHON_SITELIBDIR%%/packagekit/enums.py
+%%PYTHON_SITELIBDIR%%/packagekit/filter.py
+%%PYTHON_SITELIBDIR%%/packagekit/misc.py
+%%PYTHON_SITELIBDIR%%/packagekit/package.py
+%%PYTHON_SITELIBDIR%%/packagekit/progress.py
 libdata/pkgconfig/packagekit-glib2.pc
 libexec/packagekit-direct
 libexec/packagekitd
@@ -148,3 +148,4 @@ share/vala/vapi/packagekit-glib2.deps
 share/vala/vapi/packagekit-glib2.vapi
 /var/lib/PackageKit/transactions.db
 @dir /var/lib/PackageKit
+@dir /var/lib