Strong -1 on this.  For zero benefit, this breaks everything (within Python and third-party code) that ever relied on the documented behavior , https://docs.python.org/3/c-api/long.html#c.PyLong_AsUnsignedLong .

The cause perfectly fits the definition of an OverflowError:

class OverflowError(ArithmeticError)
 |  Result too large to be represented.

The time to challenge API design decisions is when they are created, not after they've been published and relied upon for over decade.

Also, we really don't everyone who writes cross-platform code and tests to have to catch both exceptions because they don't know which version is being run.  This creates yet another barrier to upgrading Python and as far as I can tell isn't solving any reported user problem.  Instead, it is second-guessing design decisions made long ago.