*I'm* not suggesting using Popen.  That would be a more significant change to the code, and I don't see a motivation for it.  I'm just suggesting using list2cmdline for the quoting.  (If we were rewriting distutils it would be a different story, but we're not.)

And no, Popen with shell=True does *not* handle quoting.  If you use shell=True, *you* are responsible for doing correct quoting (and is what makes using shell=True so dangerous).  That applies to both unix and windows, and the confusion about that fact was what led to the need for the "fix" backout in issue 8972.

If a fix can't go in as a bug fix (whether or not it gets into 3.5.0), then we should perhaps instead consider the rewrite for 3.6: provide a *new* distutils function that does use Popen and does things "right" (based on everything we've learned since distutils was written), leaving the old function in place, deprecated, for backward compatibility.

That doesn't solve the problem for people running in to this bug trying to build extensions for 2.7, 3.4, and 3.5, though.