Code to rerun JECs on the fly

I've used Josh/Isobel's @jjswan33 @isobelojalvo code to write a very similar method that reruns on the MC pattuples with the new JEC's but make_ntuples.py has been failing with a 'ProductNotFound' error.

Command: ./make_ntuples_cfg.py channels=zh rerunFSA=1 rerunMVAMET=1 svFit=1 rerunJetsMC=1 'inputFiles=file:/hdfs/store/user/tapas/DYJetsToLL_M-50_TuneZ2Star_8TeV-madgraph-tarball/Summer12_DR53X-PU_S10_START53_V7A-v1/AODSIM/2013-03-13-8TeV-53X-PatTuple_Master/patTuple_cfg-00037C53-AAD1-E111-B1BE-003048D45F38.root'

Error:
An exception of category 'ProductNotFound' occurred while
   [0] Processing run: 1 lumi: 40866 event: 16333208
   [1] Running path 'rerun_JetsMC'
   [2] Calling event method for module PileupJetIdProducer/'pileupJetIdProducer'
Exception Message:
getByLabel: Found zero products matching all criteria
Looking for sequence of type: reco::Jet
Looking for module label: selectedPatJetsPFlow
Looking for productInstanceName: 
   Additional Info ...

Any idea what the problem might be here? I'm playing with what is essentially a black box to me atm so any help is very much appreciated.

Stephane