> In my opinion the check for \r should only happen when os.linesep or
> newline starts with \r. On Unix with standard newline the \r should be
> treated as every other char.

No: it is not dependent on os.linesep but on the newline parameter
passed to open().
It's perfectly valid to want to read a file with CRLF endings on Unix
(Amaury's patches end up in my /tmp directory like that.)