When attempting to reprocess some hsc data, I ran into a number of problems (one fixed in
DM-8822). In this case, some of the python type definition in the obs_subaru Mapper.paf files are not valid: __builtin__.str doesn't exist on python3. Fortunately because of our use of futurize, we have builtins.str.
Although I don't plan to write it as part of this ticket, having a python2+3 validation system for the policy files would be good.