This is necessary because when Python is initialized, it takes the codec to use from GetConsoleCP() and GetConsoleOutputCP() without bothering to check whether the given codec is available. However, in most cases, the console codepage will be the same as the ANSI codepage (ie. GetACP()) which is always supported by Python via the 'mbcs' codec.
So what we do is we check whether the console codepage is frozen in, and if not, we set the console codepage to the ANSI codepage and set the stdin/stdout/stderr encoding to 'mbcs'.
This is still not a perfect solution because the ACP may not be able to encode all characters that the application is printing, which would still result in unexpected errors. Ideally, we'd pull in Python 3.6's _io._WindowsConsoleIO class, which bypasses this whole mess by directly using the wide-character Windows APIs to write to the console.
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