adapt the python 3.7 ast additions/changes

[RonnyPfannschmidt]

python3.7 did away with pyo and it did add/change some details about the ast

this causes the current failures and should be reasonably fixabl

[tomviner]

python3.7 did away with pyo

wasn't that in 3.5? https://www.python.org/dev/peps/pep-0488/

[RonnyPfannschmidt]

@tomviner thanks correcting - i misinterpreted the pr output back then

[Perlence]

Alpha versions of Python 3.7.0 don't respect PYTHONDONTWRITEBYTECODE https://bugs.python.org/issue31845
This makes test_dont_write_bytecode fail.

[Perlence]

Looks like PYTHONOPTIMIZE has no effect either.

[nicoddemus]

Thanks @Perlence for finding this.