Dropped use of depricated python3-setuptools / distutils.

Make sure sysconfig.get_path("platlib") return correct path on Debian
and Ubuntu systems, where /usr/lib/ should be used over
/usr/local/lib.

Based on e2c10a8 by Andy Pugh,

Fixes Debian issue #1080668.

src/configure.ac

@@ -1653,7 +1653,24 @@ fi
 AC_MSG_RESULT([$PYTHON_TK_VERSION])
 
 AC_MSG_CHECKING(for site-package location)
-SITEPY=`$PYTHON -c 'import distutils.sysconfig; print(distutils.sysconfig.get_python_lib())'`
+case "$(lsb_release -is)" in
+    Debian|Ubuntu)
+
+	# Setting DEB_PYTHON_INSTALL_LAYOUT adjust sysconfig 'platlib' path, see
+	# <URL: https://bugs.debian.org/1080668 >.  This affect SITEPY and
+	# might also affect AX_PYTHON and AX_PYTHON_DEVEL.
+
+	# The sed replacing python3.7 and similiar with python3 is to
+	# work with buster, which return version specific path.
+	# The sed replacing site-package to work with bullseye and
+	# older, which return ../site-packages, not .../dist-packages.
+	export DEB_PYTHON_INSTALL_LAYOUT=deb
+	SITEPY="$($PYTHON -c 'import sysconfig; import re; p2=sysconfig.get_path("platlib").replace("/site-packages", "/dist-packages"); print(re.sub(r"/python3[\.\d]+/","/python3/u", p2))')"
+	;;
+    *)
+	SITEPY=`$PYTHON -c 'import distutils.sysconfig; print(distutils.sysconfig.get_python_lib())'`
+	;;
+esac
 AC_MSG_RESULT($SITEPY)
 
 AC_MSG_CHECKING(for working GLU quadrics)

src/m4/ax_python.m4

@@ -64,7 +64,7 @@ if test x$ax_python_bin != x; then
      AC_CHECK_LIB(${ax_python_bin}m, main, ax_python_lib=${ax_python_bin}m, ax_python_lib=no)
    fi
    if test x$ax_python_lib != xno; then
-     ax_python_header=`$ax_python_bin -c "from distutils.sysconfig import *; print(get_config_var('CONFINCLUDEPY'))"`
+     ax_python_header=`$ax_python_bin -c "import sysconfig; print(sysconfig.get_path('include'))"`
      if test x$ax_python_header != x; then
        break;
      fi

src/m4/ax_python_devel.m4

@@ -186,34 +186,23 @@ variable to configure. See ``configure --help'' for reference.
 	   fi
 	fi
 
-	if test $ax_python_devel_found = yes; then
-	   #
-	   # Check if you have distutils, else fail
-	   #
-	   AC_MSG_CHECKING([for the sysconfig Python package])
-	   ac_sysconfig_result=`$PYTHON -c "import sysconfig" 2>&1`
-	   if test $? -eq 0; then
+	#
+	# Check if you have sysconfig, else fail
+	#
+	AC_MSG_CHECKING([for the sysconfig Python package])
+	ac_sysconfig_result=`$PYTHON -c "import sysconfig" 2>&1`
+	if test $? -eq 0; then
 		AC_MSG_RESULT([yes])
 		IMPORT_SYSCONFIG="import sysconfig"
-	   else
-		AC_MSG_RESULT([no])
-
-		AC_MSG_CHECKING([for the distutils Python package])
-		ac_sysconfig_result=`$PYTHON -c "from distutils import sysconfig" 2>&1`
-		if test $? -eq 0; then
-			AC_MSG_RESULT([yes])
-			IMPORT_SYSCONFIG="from distutils import sysconfig"
-		else
-			AC_MSG_WARN([cannot import Python module "distutils".
+	else
+        AC_MSG_ERROR([cannot import Python module "sysconfig".
 Please check your Python installation. The error was:
 $ac_sysconfig_result])
 			if ! $ax_python_devel_optional; then
 			   AC_MSG_ERROR([Giving up])
 			fi
 			ax_python_devel_found=no
 			PYTHON_VERSION=""
-		fi
-	   fi
 	fi
 
 	if test $ax_python_devel_found = yes; then
@@ -228,12 +217,6 @@ $ac_sysconfig_result])
 				print (sysconfig.get_path ('include'));"`
 			plat_python_path=`$PYTHON -c "$IMPORT_SYSCONFIG; \
 				print (sysconfig.get_path ('platinclude'));"`
-		else
-			# old distutils way
-			python_path=`$PYTHON -c "$IMPORT_SYSCONFIG; \
-				print (sysconfig.get_python_inc ());"`
-			plat_python_path=`$PYTHON -c "$IMPORT_SYSCONFIG; \
-				print (sysconfig.get_python_inc (plat_specific=1));"`
 		fi
 		if test -n "${python_path}"; then
 			if test "${plat_python_path}" != "${python_path}"; then