fix to move to rivet 2.1.2

[mkirsano]

No description provided.

[cmsbuild]

A new Pull Request was created by @mkirsano for CMSSW_7_2_X.

fix to move to rivet 2.1.2

It involves the following packages:

GeneratorInterface/RivetInterface

@vciulli, @nclopezo, @thuer, @cmsbuild, @bendavid, @Degano can you please review it and eventually sign? Thanks.
You can sign-off by replying to this message having '+1' in the first line of your reply.
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[mkirsano]

To be done simultaneously with PR cmsdist #856

[bendavid]

+1

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_2_X IBs unless changes or unless it breaks tests.

[ghost]

+1
Tested compilation manually along PR cms-sw/cmsdist#856

[cmsbuild]

This pull request is fully signed and it will be integrated in one of the next CMSSW_7_2_X IBs unless changes (tests are also fine).