[Rivet] python2 change

[David Grellscheid]

Hi Andy,

> PS. Riveteers, I note that Hannes' Mac has explicit /usr/bin/python2,3
> executables, as do the Ubuntu and SL installations checked by Frank and
> myself. So unless there are objections I suggest that we move to
> explicitly invoking "python2" rather than "python" in our Rivet (and
> YODA) scripts from the next release.

Please don't hide requests like this at the bottom of other topics.

The change is not going to work on OS X, since there is no python2
symlink. You have to explicitly specify the second digit.

  David