main/python3: mark python package dir as externally-managed again

now that latest ubuntu/debian forbid this too, and pipx exists to easily
install things into a venv, we should do the same.

reverts f57181f6
reinstates 40d10fdd

main/python3/APKBUILD

@@ -4,7 +4,7 @@ pkgname=python3
 # the python3-tkinter's pkgver needs to be synchronized with this.
 pkgver=3.11.4
 _basever="${pkgver%.*}"
-pkgrel=1
+pkgrel=2
 pkgdesc="High-level scripting language"
 url="https://www.python.org/"
 arch="all"
@@ -40,6 +40,7 @@ makedepends="
 	zlib-dev
 	"
 source="https://www.python.org/ftp/python/$pkgver/Python-$pkgver.tar.xz
+	externally-managed
 	musl-find_library.patch
 	"
 options="net" # Required for tests
@@ -179,6 +180,9 @@ package() {
 	make -j1 DESTDIR="$pkgdir" EXTRA_CFLAGS="$CFLAGS" install maninstall
 	install -Dm644 LICENSE "$pkgdir"/usr/share/licenses/$pkgname/LICENSE
 
+	install -Dm644 "$srcdir"/externally-managed \
+		"$pkgdir"/usr/lib/python$_basever/EXTERNALLY-MANAGED
+
 	# those are provided by python3-tkinter
 	rm -r "$pkgdir"/usr/bin/idle* "$pkgdir"/usr/lib/python*/idlelib \
 		"$pkgdir"/usr/lib/python*/tkinter
@@ -249,5 +253,6 @@ pyc2() {
 
 sha512sums="
 7eb14fecbf60824d10c22a9057584c3a142c2866f4af6caa2525c10c8bcb24e6e7afb32a44a0e118df0a2b2543d578c3b422ffd4a5fa317dfe6ea371cc7ee1ee  Python-3.11.4.tar.xz
+46dd8230ee2ab66e9c4157c10b2bd9c414fd7f30be0bee73e21a9eea88f63fff362d47828e0fc77ddc59df097b414b21505f8b5f98bc866381115c58ae3f4862  externally-managed
 ab8eaa2858d5109049b1f9f553198d40e0ef8d78211ad6455f7b491af525bffb16738fed60fc84e960c4889568d25753b9e4a1494834fea48291b33f07000ec2  musl-find_library.patch
 "

main/python3/externally-managed

+[externally-managed]
+Error=
+ The system-wide python installation should be maintained using the system
+ package manager (apk) only.
+
+ If the package in question is not packaged already (and hence installable via
+ "apk add py3-somepackage"), please consider installing it inside a virtual
+ environment, e.g.:
+
+   python3 -m venv /path/to/venv
+   . /path/to/venv/bin/activate
+   pip install mypackage
+
+ To exit the virtual environment, run:
+
+   deactivate
+
+ The virtual environment is not deleted, and can be re-entered by re-sourcing
+ the activate file.
+
+ To automatically manage virtual environments, consider using pipx (from the
+ pipx package).