Thanks for the report and thanks for the PR.  I am confused here as I cannot reproduce the failure.  Can someone show what is invalid in the Makefile?  Also, if the change really does need to be made to Setup.dist (3.7) or Setup (master -> 3.8), then setup.py should likely be changed to reduce future confusion (although it presumably doesn't make a difference to the compile).  Further, please submit PRs like this against the master branch (unless the problem only exists in a specific released branches); fixes are normally applied to the master branch and the core developer handling the merge will elect to backport to appropriate branches as needed.