build-sys: explicitly require python3

Otherwise python programs might be run with python2

diff --git a/configure.ac b/configure.ac
index 5979de4dc6a9ffa9a8c0575ca3a50bbf1e169eb9..32febcabe9d21ef25cf9e42cddb5a7ff3556be91 100644 (file)
--- a/configure.ac
+++ b/configure.ac
@@ -263,7 +263,7 @@ AC_ARG_WITH([python],
 
 have_lxml=no
 AS_IF([test "x$with_python" != "xno"], [
-        AM_PATH_PYTHON(,, [:])
+        AM_PATH_PYTHON([3],, [:])
         AS_IF([test "x$PYTHON" != "x:"], [
                 AC_MSG_CHECKING([for python lxml module])
                 AS_IF(["$PYTHON" -c 'import lxml' 2>/dev/null], [have_lxml=yes])