Im concerned about this change, as VS 2015 cannot build v141 binaries. I know v141 is binary compatible with v140, but shouldn't the VS version that builds Python stay consistent in a minor release? Or at least, shouldn't this be discussed more before this change is made? It requires the user to update VS which is a non-trivial change.

Ah, I see this seems to support both. Great!

@ethanhs It shouldn't require any update for existing users - VS 2015 can be used to build v140 binaries which are compatible with v141. This is why I explicitly enabled both versions of VS in AppVeyor.

But I did briefly forget about Tcl/Tk not supporting VS 2017 builds... guess we can't backport this change after all.

@zooba thanks, "Change to building with MSVC v141" sounds like "replace v140 with v141" so I was concerned. Too bad this cannot be backported :(

Trying again - I merged the fix for Tcl/Tk into master and merged it into this branch, so we should have success now.