Correct a flaw in the Python 3 version checking (openzfs#12636)

It turns out the ax_python_devel.m4 version check assumes that
("3.X+1.0" >= "3.X.0") is True in Python, which is not when X+1
is 10 or above and X is not. (Also presumably X+1=100 and ...)

So let's remake the check to behave consistently, using the
"packaging" or (if absent) the "distlib" modules.

(Also, update the Github workflows to use the new packages.)

Reviewed-by: Brian Behlendorf <behlendorf1@llnl.gov>
Reviewed-by: John Kennedy <john.kennedy@delphix.com>
Signed-off-by: Rich Ercolani <rincebrain@gmail.com>
Closes: openzfs#12073

.github/workflows/zfs-tests-functional.yml

@@ -26,7 +26,7 @@ jobs:
           xfslibs-dev libattr1-dev libacl1-dev libudev-dev libdevmapper-dev \
           libssl-dev libffi-dev libaio-dev libelf-dev libmount-dev \
           libpam0g-dev pamtester python-dev python-setuptools python-cffi \
-          python3 python3-dev python3-setuptools python3-cffi
+          python3 python3-dev python3-setuptools python3-cffi python3-packaging
     - name: Autogen.sh
       run: |
         sh autogen.sh

.github/workflows/zfs-tests-sanity.yml

@@ -22,7 +22,7 @@ jobs:
           xfslibs-dev libattr1-dev libacl1-dev libudev-dev libdevmapper-dev \
           libssl-dev libffi-dev libaio-dev libelf-dev libmount-dev \
           libpam0g-dev pamtester python-dev python-setuptools python-cffi \
-          python3 python3-dev python3-setuptools python3-cffi
+          python3 python3-dev python3-setuptools python3-cffi python3-packaging
     - name: Autogen.sh
       run: |
         sh autogen.sh

.github/workflows/zloop.yml

@@ -22,8 +22,8 @@ jobs:
           xfslibs-dev libattr1-dev libacl1-dev libudev-dev libdevmapper-dev \
           libssl-dev libffi-dev libaio-dev libelf-dev libmount-dev \
           libpam0g-dev \
-          python-dev python-setuptools python-cffi \
-          python3 python3-dev python3-setuptools python3-cffi
+          python-dev python-setuptools python-cffi python-packaging \
+          python3 python3-dev python3-setuptools python3-cffi python3-packaging
     - name: Autogen.sh
       run: |
         sh autogen.sh

config/always-pyzfs.m4

@@ -46,6 +46,21 @@ AC_DEFUN([ZFS_AC_CONFIG_ALWAYS_PYZFS], [
 	])
 	AC_SUBST(DEFINE_PYZFS)
 
+	dnl #
+	dnl # Python "packaging" (or, failing that, "distlib") module is required to build and install pyzfs
+	dnl #
+	AS_IF([test "x$enable_pyzfs" = xcheck -o "x$enable_pyzfs" = xyes], [
+		ZFS_AC_PYTHON_MODULE([packaging], [], [
+			ZFS_AC_PYTHON_MODULE([distlib], [], [
+				AS_IF([test "x$enable_pyzfs" = xyes], [
+					AC_MSG_ERROR("Python $PYTHON_VERSION packaging and distlib modules are not installed")
+				], [test "x$enable_pyzfs" != xno], [
+					enable_pyzfs=no
+				])
+			])
+		])
+	])
+
 	dnl #
 	dnl # Require python-devel libraries
 	dnl #

config/ax_python_devel.m4

@@ -97,9 +97,18 @@ AC_DEFUN([AX_PYTHON_DEVEL],[
 	# Check for a version of Python >= 2.1.0
 	#
 	AC_MSG_CHECKING([for a version of Python >= '2.1.0'])
-	ac_supports_python_ver=`$PYTHON -c "import sys; \
-		ver = sys.version.split ()[[0]]; \
-		print (ver >= '2.1.0')"`
+	ac_supports_python_ver=`cat<<EOD | $PYTHON -
+from __future__ import print_function;
+import sys;
+try:
+	from packaging import version;
+except ImportError:
+	from distlib import version;
+ver = sys.version.split ()[[0]];
+(tst_cmp, tst_ver) = ">= '2.1.0'".split ();
+tst_ver = tst_ver.strip ("'");
+eval ("print (version.LegacyVersion (ver)"+ tst_cmp +"version.LegacyVersion (tst_ver))")
+EOD`
 	if test "$ac_supports_python_ver" != "True"; then
 		if test -z "$PYTHON_NOVERSIONCHECK"; then
 			AC_MSG_RESULT([no])
@@ -126,9 +135,21 @@ to something else than an empty string.
 	#
 	if test -n "$1"; then
 		AC_MSG_CHECKING([for a version of Python $1])
-		ac_supports_python_ver=`$PYTHON -c "import sys; \
-			ver = sys.version.split ()[[0]]; \
-			print (ver $1)"`
+		# Why the strip ()?  Because if we don't, version.parse
+		# will, for example, report 3.10.0 >= '3.11.0'
+		ac_supports_python_ver=`cat<<EOD | $PYTHON -
+
+from __future__ import print_function;
+import sys;
+try:
+	from packaging import version;
+except ImportError:
+	from distlib import version;
+ver = sys.version.split ()[[0]];
+(tst_cmp, tst_ver) = "$1".split ();
+tst_ver = tst_ver.strip ("'");
+eval ("print (version.LegacyVersion (ver)"+ tst_cmp +"version.LegacyVersion (tst_ver))")
+EOD`
 		if test "$ac_supports_python_ver" = "True"; then
 		   AC_MSG_RESULT([yes])
 		else

rpm/generic/zfs.spec.in

@@ -311,6 +311,11 @@ Requires:       libffi
 Requires:       python%{__python_pkg_version}
 Requires:       %{__python_cffi_pkg}
 %if 0%{?rhel}%{?fedora}%{?suse_version}
+%if 0%{?rhel} >= 8 || 0%{?centos} >= 8 || 0%{?fedora} >= 28
+BuildRequires:  python3-packaging
+%else
+BuildRequires:  python-packaging
+%endif
 BuildRequires:  python%{__python_pkg_version}-devel
 BuildRequires:  %{__python_cffi_pkg}
 BuildRequires:  %{__python_setuptools_pkg}