-- The current Nauty library is very picky about the Graph.pm module
   version. Version 0.96 (default Debian package for LinuxMint-19) is
   reported as too old, but the 0.9721 version (default in CPAN as of
   writing of this note) brings with it the Set::Object dependency and
   Object.so implementation, and causes Nauthy.so (and thus some
   automatic tests) to segfault. Only the Graph-0.9704 version
   (default on Linuxmint-20.1) works. Given that the incompatibility
   of Nauty with the 0.9721 version of the Graph is not diagnosed, the
   failing tests leave a lot of guessing as to whether the package is
   operational.

   More accurate Nauty (probably Nauty.so) compatibiliy diagnostics
   and adaptation is desirable.
