Add exec wrapper function to compat
use compat exec in pyobjects
make pydsl compile on py3
missed an exec...
lint fixes
Add exceptions module wrapper to compat

This is not in six BTW, so it we ever want to switch to six this would
need to be added
Use builtins correctly in python3
Merge pull request #17309 from thatch45/py3_compile

Get all compiles on python3