Format diff message
Format diff message

Use a more pythonic way to format the diff message.
Assume file[0] is the 'good/gold' file.

andrsd/moose,idaholab/moose,milljm/moose,SudiptaBiswas/moose,jessecarterMOOSE/moose,YaqiWang/moose,idaholab/moose,bwspenc/moose,idaholab/moose,lindsayad/moose,lindsayad/moose,harterj/moose,andrsd/moose,laagesen/moose,andrsd/moose,sapitts/moose,nuclear-wizard/moose,harterj/moose,milljm/moose,idaholab/moose,bwspenc/moose,YaqiWang/moose,milljm/moose,laagesen/moose,lindsayad/moose,jessecarterMOOSE/moose,YaqiWang/moose,laagesen/moose,milljm/moose,harterj/moose,nuclear-wizard/moose,permcody/moose,sapitts/moose,sapitts/moose,jessecarterMOOSE/moose,dschwen/moose,milljm/moose,lindsayad/moose,dschwen/moose,bwspenc/moose,SudiptaBiswas/moose,jessecarterMOOSE/moose,nuclear-wizard/moose,SudiptaBiswas/moose,bwspenc/moose,dschwen/moose,sapitts/moose,andrsd/moose,lindsayad/moose,andrsd/moose,laagesen/moose,idaholab/moose,SudiptaBiswas/moose,nuclear-wizard/moose,harterj/moose,SudiptaBiswas/moose,permcody/moose,laagesen/moose,dschwen/moose,dschwen/moose,YaqiWang/moose,harterj/moose,sapitts/moose,permcody/moose,jessecarterMOOSE/moose,bwspenc/moose,permcody/moose