regent: Make setup_env.py less brittle about calling install.py.
regent: Make setup_env.py less brittle about calling install.py.

StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion,StanfordLegion/legion