[pygobject] configure.ac: Error out in case autoconf-archive isn't installed

[Christoph Reiter <creiter src gnome org>]

commit d19aca693950c0edb02b226db8bcf81a5304870e
Author: Christoph Reiter <creiter src gnome org>
Date:   Fri Dec 8 14:40:58 2017 +0100

    configure.ac: Error out in case autoconf-archive isn't installed
    
    Check whether the AX_IS_RELEASE macro is defined and if not print
    a proper error message.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=784428

 configure.ac |    3 +++
 1 files changed, 3 insertions(+), 0 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 876681d..cdecad2 100644
--- a/configure.ac
+++ b/configure.ac
@@ -31,6 +31,9 @@ m4_define(libffi_required_version, 3.0)
 AC_INIT([pygobject],[pygobject_version],
        [http://bugzilla.gnome.org/enter_bug.cgi?product=pygobject],
        [pygobject],[https://wiki.gnome.org/Projects/PyGObject/])
+
+m4_ifndef([AX_IS_RELEASE], [AC_MSG_ERROR(['autoconf-archive' missing])])
+
 AX_IS_RELEASE([minor-version])
 AC_CONFIG_MACRO_DIR([m4])
 AC_CONFIG_SRCDIR([gi/gimodule.c])