clean weight names before passing GenEvent to Rivet
@akelly has discovered that Rivet3 cannot deal with the non-canonical weight names used by Powheg e.g. in the baseline ttbar sample. Weight names like
' PDF set = 260093 ',
' 0p5muF_2muR_CT14 ',
' nominal '
are really not acceptable, but seeing as the sample cannot easily be re-generated, we will need to clean the weight names before passing the GenEvent to Rivet.
All a bit hacky, but seems to work.