[master] 49712a5 vmods running vmodtool require python, so check for it

[Nils Goroll]

commit 49712a5fae5919e6e333d7164b98ef986b149c62
Author: Nils Goroll <nils.goroll at uplex.de>
Date:   Thu May 21 19:21:28 2015 +0200

    vmods running vmodtool require python, so check for it
    
    (even if we exec env python, we should check early if we got one)

diff --git a/varnish.m4 b/varnish.m4
index 8339cb0..b7ad6f9 100644
--- a/varnish.m4
+++ b/varnish.m4
@@ -81,6 +81,10 @@ AC_SUBST([VMOD_DIR])
 
 AC_DEFUN([VARNISH_VMODTOOL],
 [
+AC_CHECK_PROGS(PYTHON, [python3 python3.1 python3.2 python2.7 python2.6 python2.5 python2 python], "no")
+if test "x$PYTHON" = "xno"; then
+  AC_MSG_ERROR([Python is needed to build, please install python.])
+fi
 VARNISH_PKG_GET_VAR([VMODTOOL], [vmodtool])
 AC_SUBST([VMODTOOL])
 ])