Note that python -m pip works, which is what indicates to me that it's the launcher that is having the problem with the space in the path.
Okay, it looks like a change in distlib to put quotes around paths with spaces in them is conflicting with the launcher doing the same thing - hence the double quotes. It would seem like the correct fix would be for the launcher not to add quotes if some are already there.
BTW Alex, props for APScheduler :-)
@Paul Moore I've updated the launchers in 07d0757 to avoid double-quoting. I'd appreciate it if you could verify if this fixes the problem.
Hmm, I cannot reproduce the original issue on the PC I am using at the moment. I'll try to reproduce, and then test the fix, on Monday.
OK, got it reproduced on my other PC, and this fix sorts out the issue. I'm not sure why it only happens on one of the PCs, but I guess that's less important.
@Alex Grönholm Once we get a new distlib release, this will go into pip and then into virtualenv, so it won't appear as a resolution for your issue till then.