Worked for a bit debugging this issue today, and while we never got to the root cause, we did get enough information to determine how to avoid such slowness, which is to avoid running setup.py from a directory in a git-svn checkout.
<rdar://problem/67120623>
Created attachment 406656 [details] Patch
Comment on attachment 406656 [details] Patch Waiting for Dean, who originally reported the issue with his configuration, to verify this actually fixes things for him.
(In reply to Jonathan Bedard from comment #3) > Comment on attachment 406656 [details] > Patch > > Waiting for Dean, who originally reported the issue with his configuration, > to verify this actually fixes things for him. Dean verified that this fixed his issue. Seems like setup.py doesn't like running from git-svn checkouts.
Comment on attachment 406656 [details] Patch Unofficial r+; fixes my issue and code / ChangeLog looks good.
Committed r265766: <https://trac.webkit.org/changeset/265766> All reviewed patches have been landed. Closing bug and clearing flags on attachment 406656 [details].