The function stat.filemode() has a fallback to "-" for file type when it is unable to properly detect the type of a file. This gives wrong results for any file type that is not in the lookup table.

For example it doesn't check for S_ISSOCK:

>>> s = os.stat("/var/run/sdp") t
>>> stat.filemode(s.st_mode)
'-rw-rw-rw-'
$ ls -la /var/run/sdp
srw-rw-rw- 1 root root 0 Mai  2 16:08 /var/run/sdp

Also see #11016 for more file types.

I'm going to work on the matter soonish.