This is beginning to look like it is an issue with the version of automake installed: 

aixtools@gcc119:[/home/aixtools/cpython/cpython-master]automake --version
Unescaped left brace in regex is deprecated, passed through in regex; marked by <-- HERE in m/\${ <-- HERE ([^ \t=:+{}]+)}/ at /usr/bin/automake line 3936.
automake (GNU automake) 1.15
Copyright (C) 2014 Free Software Foundation, Inc.
License GPLv2+: GNU GPL version 2 or later <http://gnu.org/licenses/gpl-2.0.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

Written by Tom Tromey <tromey@redhat.com>
       and Alexandre Duret-Lutz <adl@gnu.org>.


Will test on a system where I can install the latest automake.

Assuming an updated version of automake fixes that - but not knowing autotools well enough - is there a simple addition to ensure that automake-1.16 is used?