move the NO return value to the except block
PEPify python executor, retab
drop use of Python framework, update project setting as suggested by Xcode 6

https://developer.apple.com/library/mac/technotes/tn2328/_index.html
import Python header unix-style, drop precompile prefix header setting
merge update in Python executor
Merge branch 'update_xcproject'
ignore user specific setting in Xcode project