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Since WindowsError became an alias of OSError, the error number shown in the stringification of an OSError err can either be a windows error code (err.winerror) or a posix style error number (err.errno), with no way to tell which.
For instance in
 >>> os.read(999, 0)
 Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 OSError: [Errno 9] Bad file descriptor
err.errno == EBADF == 9 and err.winerror == None, but in
 >>> _winapi.ReadFile(999, 0)
 Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 OSError: [Error 6] The handle is invalid
err.errno == EBADF == 9 and err.winerror == ERROR_INVALID_HANDLE == 6. (winerror gets priority over errno if it exists.)
With the attached patch the second will be shown as
 >>> _winapi.ReadFile(999, 0)
 Traceback (most recent call last):
 File "<stdin>", line 1, in <module>
 OSError: [WinError 6] The handle is invalid
 ^^^
Since this issue only applies to 3.3 and the patch is trivial, it would be nice to get this in before 3.3 is released.