GeezerVison

Out of interest, what would it look like to make those imports conditional? They ought to be anyway, and I suspect we'll end up with better overall behaviour if they handle this as "no registry access exists" rather than "registry accesses always fail".

I don't really know how it would be done because it requires modifying a lot of Python code and introduce helper functions or constants to identify UWP / GAMES builds as "another platform". This is beyond the scope of this PR.

In addition to this, I want to avoid modifying the behavior of MS_WINDOWS_GAMES builds because I have no easy way to test it (nor any particular interest).

This PR allows compile the current code for UWP and is actually a simplification because it removes 185 lines of code. Without this PR, the resulting UWP builds won't work because they try to import a module that doesn't exist --> hard crash.

With this PR, you can use the rest of the Python code in UWP, and even if a Python script includes import winreg lines and the the script handles the exceptions, return values, etc. nothing bad happens.

Previously, Windows Registry was available for "Windows Phone" in the MS_WINDOWS_APP partition, and most of the Win32 Registry API is still defined. This is why compile winreg.c code for MS_WINDOWS_APP/GAMES is possible and doesn't produce errors. I'm not actually sure if accessing the Registry outside of classic Desktop environment is still useful on other types of devices (Surface or ARM64 devices).

Having had a quick look, it seems like Lib\importlib\_bootstrap_external.py is the only one that needs handling. getpath.py and the rest of the standard library uses are protected (apart from one in IDLE, which I assume you don't care about).

Some of the test suite also assumes the module will be there, and those ought to be handled either at the winreg import or the command importing the module that requires it.

There's no need to modify anything conditionally on the build, it's just going to be something like:

try:
    import winreg
except ImportError:
    winreg = None

...

if winreg:
    # do the thing requiring the registry
else:
    # fallback behaviour if needed

For _bootstrap_external.py I think it's just an entire block that's already optional for non-Windows, so that can become for non-winreg, and it should be good.

Having had a quick look, it seems like Lib\importlib_bootstrap_external.py is the only one that needs handling.

try:
    import winreg
except ImportError:
    winreg = None

Tested this change on UWP build and works fine and seems is enough. I'm going to update the PR with this.