Cygwin had an issue with building and installing python after it was configured. The main issue was the TLS key stuff which would make python fail to fully build or work correctly. This issue contains a patch for cygwin specifically to make it compile and work fully. It uses the __CYGWIN__ macro for separating the code from this patch with the TLS code on the other targets. This should help fix issues that was present in the standard library and setup.py in the repo for cygwin as well.