IDL compiler: sync Python to r163178

Python side to:
WIP: Migrate generated bindings to new ExceptionState constructor.
https://codereview.chromium.org/99083002/

Also 2 FIXMEs due to minor errors in original Perl CL,
which I'll fix in a separate CL: this is Python-only.

BUG=239771
NOTRY=true
TBR=haraken

Review URL: https://codereview.chromium.org/105883006

git-svn-id: svn://svn.chromium.org/blink/trunk@163205 bbb929c8-8fbe-4397-9dbb-9b2b20218538