Hi @gyoice88.
You can try increasing the value of gErrorIgnoreLevel as suggested in this post to 6001 or directly to kFatal. Remember that in Python ROOT global variables are accessible under the ROOT module, e.g.
ROOT.gErrorIgnoreLevel = ROOT.kFatal
Then
Does this mean that you do not want to use python2 ? Have you built ROOT with python2 perhaps?
But from the path you posted /root-6.20.04/... it seems to me you’re not. Since ROOT 6.22 we support multi-python builds, e.g. if your system has both python2 and 3 ROOT will be built with support for both versions. Find more information at ROOT, Python and PyROOT.