Using os.path.realpath(...) in the MVFS of Clearcase SCM (virtual file system) in Windows 10 a exception occures:

X:\my_view\tools\python\3_8>python.exe
Python 3.8.5 (tags/v3.8.5:580fbb0, Jul 20 2020, 15:57:54) [MSC v.1924 64 bit (AMD64)] on win32
Type "help", "copyright", "credits" or "license" for more information.
>>> import os
>>> os.path.realpath('.')
Traceback (most recent call last):
  File "X:\my_view\tools\python\3_8\lib\ntpath.py", line 647, in realpath
    path = _getfinalpathname(path)
OSError: [WinError 87] Falscher Parameter: 'X:\\my_view\\tools\\python\\3_8\\.'

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "X:\my_view\tools\python\3_8\lib\ntpath.py", line 651, in realpath
    path = _getfinalpathname_nonstrict(path)
  File "X:\my_view\tools\python\3_8\lib\ntpath.py", line 601, in _getfinalpathname_nonstrict
    path = _getfinalpathname(path)
FileNotFoundError: [WinError 161] Der angegebene Pfadname ist ungültig: 'X:\\'
>>> 

The error 161 (ERROR_BAD_PATHNAME) should also be ignored in _getfinalpathname_nonstrict.

It should also ignore ERROR_BAD_NETPATH (53).

Updated with ERROR_BAD_NETPATH (53).
What about following errors:
- ERROR_LOCK_VIOLATION (33)
- ERROR_DEV_NOT_EXIST (52)
- ERROR_BAD_NET_RESP (58)
- ERROR_UNEXP_NET_ERR (59)
- ERROR_NETNAME_DELETED (64)
- ERROR_NETWORK_ACCESS_DENIED (65)
- ERROR_BAD_DEV_TYPE (66)

ERROR_NETWORK_ACCESS_DENIED (65) should probably be added to the ignore list. I don't know whether it occurs in practice, but we have it mapped to EACCES in PC/errmap.h. The common access error is ERROR_ACCESS_DENIED (5), even on a UNC share with restricted access.

Add ERROR_DEV_NOT_EXIST (55) only if you have a case that fails with this error code. It's from the NT status code STATUS_DEVICE_DOES_NOT_EXIST. This might occur when trying to automount a device that's pending removal (see the implementation in ReactOS IopMountVolume [1]), but I can't create this condition. I think a device object would need to be practically stuck in the pending removal state for this to be a practical problem.

ERROR_LOCK_VIOLATION (33) isn't relevant. It's an I/O access error for a locked range of a file. realpath() doesn't read or write file data.

For the others, I'd wait for an issue to be reported. 

---

[1] https://github.com/reactos/reactos/blob/master/ntoskrnl/io/iomgr/volume.c#L457

Done.