This does notfix#127257 but would have made it easier to debug.

• To make it easier to vary the individual parts of the message,
  replace the if-ladder with a few constant format strings by
  building the string piece-wise using PyUnicodeWriter.

• Use "unknown error (0x%x)" rather than just "unknown error"
  if we can't get a better error message. (Hex makes sense as
  the error includes two byte-packed parts.)

As there are no cases where weshould raise an "unknown error",
I don't see a good way to add tests. But, we can verify using the
current failure on Arch Linux buildbots.
Existing tests do cover error messages.

• Issue:[tests] test_poplib fails with "env changed" on Arch Linux with OpenSSL 3.4: [SYS] unknown error (_ssl.c:2634) #127257