rootpy script: use find_files in sum() to avoid limit on number of cmd args
rootpy script: use find_files in sum() to avoid limit on number of cmd args

ndawe/rootpy,kreczko/rootpy,kreczko/rootpy,rootpy/rootpy,kreczko/rootpy,ndawe/rootpy,rootpy/rootpy,rootpy/rootpy,ndawe/rootpy