[Rivet] Rivet 2.1.0 -> testing ~today?

[David Grellscheid]

Hi Andy,

> One last thing: there is a Jenkins failure since the recent changes. I
> can't reproduce the make check failures and the reported output doesn't
> look "normal": a machine problem? We should know.

It's an issue with HepMC 2.5 I have on that machine. If someone else
succeeds with HepMC 2.5 on Ubuntu, I'm happy to discard this error as an
outlier, since HepMC 2.6 and 2.4 work fine.

  David