From fa94ef0412c4f24d49aa6dfbd15e3634d52d1ff5 Mon Sep 17 00:00:00 2001
From: Christian Heimes <cheimes@redhat.com>
Date: Thu, 22 Feb 2018 15:02:56 +0100
Subject: [PATCH] autoconf prefers Python 3 over 2

The configure script now looks for Python 3.6 or newer, then falls back
to Python 2. All Makefile default to Python 3 if Python 3 is available.

See: pagure.io/freeipa/issue/7131
Signed-off-by: Christian Heimes <cheimes@redhat.com>
Reviewed-By: Alexander Bokovoy <abokovoy@redhat.com>
---
 configure.ac | 33 ++++++++++++++++++---------------
 1 file changed, 18 insertions(+), 15 deletions(-)

diff --git a/configure.ac b/configure.ac
index 4b661ecef..50371434a 100644
--- a/configure.ac
+++ b/configure.ac
@@ -100,27 +100,28 @@ PKG_CHECK_MODULES([CRYPTO], [libcrypto])
 
 dnl ---------------------------------------------------------------------------
 dnl - Check for Python
-dnl ---------------------------------------------------------------------------
-
-AC_MSG_NOTICE([Checking for Python])
-have_python=no
-AM_PATH_PYTHON(2.7)
-
-if test "x$PYTHON" = "x" ; then
-  AC_MSG_ERROR([Python not found])
-fi
-
-dnl ---------------------------------------------------------------------------
 dnl - Check for Python 2/3 for devcheck
 dnl ---------------------------------------------------------------------------
 
+AC_MSG_NOTICE([Checking for Python 3])
+AC_PATH_PROG(PYTHON3, python3)
+AC_SUBST([PYTHON3])
+AM_CONDITIONAL([WITH_PYTHON3], [test "x${PYTHON3}" != "x"])
+
+AC_MSG_NOTICE([Checking for Python 2])
 AC_PATH_PROG(PYTHON2, python2)
 AC_SUBST([PYTHON2])
 AM_CONDITIONAL([WITH_PYTHON2], [test "x${PYTHON2}" != "x"])
 
-AC_PATH_PROG(PYTHON3, python3)
-AC_SUBST([PYTHON3])
-AM_CONDITIONAL([WITH_PYTHON3], [test "x${PYTHON3}" != "x"])
+if test \( "x${PYTHON3}" = "x" -o "x${PYTHON}" != "x" \); then
+    dnl Python 3 is not available *or* user has set PYTHON variable.
+    dnl Accept Python >= 2.7 as default Python. We also accept any Python 3
+    dnl version from PYTHON environment variable.
+    AM_PATH_PYTHON(2.7)
+elif test "x${PYTHON3}" != "x"; then
+    dnl Found Python 3, but no user override. Use Python >= 3.6 as default.
+    AM_PATH_PYTHON(3.6)
+fi
 
 dnl ---------------------------------------------------------------------------
 dnl - Check for cmocka unit test framework http://cmocka.cryptomilk.org/
@@ -590,7 +591,9 @@ echo "
         source code location:     ${srcdir}
         compiler:                 ${CC}
         cflags:                   ${CFLAGS}
-        Python:                   ${PYTHON}
+        Default Python:           ${PYTHON} (${PYTHON_VERSION})
+        Python 2:                 ${PYTHON2}
+        Python 3:                 ${PYTHON3}
         pylint:                   ${PYLINT}
         jslint:                   ${JSLINT}
         LDAP libs:                ${LDAP_LIBS}