This change has the adverse side effect of requiring users of Python 3.5 to use the Visual Studio 2015 runtime library. Further, as is documented on Microsoft's website, the minimum system requirements for installing and running this runtime is Windows 7 SP1 or newer.

As a result, adopting this new compiler for the Python runtime prevents users of operating systems older than this from using this version. Even users with Windows 7 pre service pack are unable to use it. Based on a quick review of the comment thread here, the choice for adopting the 2015 compiler was relatively arbitrary and thus an older version, say 2013 for example, could have been used instead and older operation systems would still be supported with little to no impact on Python.

While this is unfortunate to say the least, what makes matters worse is there appears to be little to no information on the Python.org website indicating that the minimum system requirements have now been affected in this way. Also, for users attempting to install v3.5 on a system older than this are presented with a cryptic error message basically just saying that "some unknown error has occurred", leaving them scratching their head trying to figure out what's wrong.

Seeing as how you can't go back in time and fix this in 3.5.0, I am hoping that at the very least you could add some information about this to some obvious location on the main Python.org website, and maybe consider updating the installation for future 3.5.x releases such that a check is done to see if the operating system meets these new minimum requirements and present the user with some helpful information that would lead them to a resolution.