Permission denied with JUPYTER_PATH

[sjusko]

I have added environment variable "JUPYTER_PATH" with custom locations in Jupyterhub config file (jupyterhub_config.py) via:

c.Spawner.environment = {'JUPYTER_PATH':'/tmp/test_kernels/others/share/jupyter:/tmp/test_kernels/testuser/share/jupyter'}

Kernels are visible in Jupyterhub, but it isn't possible to start any Kernel. Even Kernels located in default locations (~/.local/share/jupyter/, {sys.prefix}/share/jupyter/) are showing "error starting kernel, unhandled error".

Issue is related to directory permissions, when user has no privileges to access one of the directories specified via "JUPYTER_PATH":

(base) [root@td-cdp kernels]# ll /tmp/test_kernels/
total 8
drwxr-xr-x 3 otheruser otheruser 4096 Dec 3 13:20 others
drwx------ 3 testuser testuser 4096 Dec 3 13:04 testuser

Following error is in logs:

File "/opt/miniconda3/lib/python3.8/site-packages/jupyter_client/kernelspec.py", line 234, in get_kernel_spec
Dec 4 14:24:28 td-cdp jupyterhub: resource_dir = self._find_spec_directory(kernel_name.lower())
Dec 4 14:24:28 td-cdp jupyterhub: File "/opt/miniconda3/lib/python3.8/site-packages/jupyter_client/kernelspec.py", line 206, in _find_spec_directory
Dec 4 14:24:28 td-cdp jupyterhub: files = os.listdir(kernel_dir)
Dec 4 14:24:28 td-cdp jupyterhub: PermissionError: [Errno 13] Permission denied: '/tmp/test_kernels/testuser/share/jupyter/kernels'
Dec 4 14:24:28 td-cdp jupyterhub: [W 2020-12-04 14:24:28.441 SingleUserNotebookApp handlers:613] Unhandled error
Dec 4 14:24:28 td-cdp jupyterhub: [E 2020-12-04 14:24:28.442 SingleUserNotebookApp log:166]

Jupyter_client is handling only "errno.ENOTDIR (Not a directory)" and "errno.ENOENT (No such file or directory)", but there is no handling for "errno.EACCES (Permission denied)".
jupyter_client/kernelspec.py:

204 for kernel_dir in self.kernel_dirs:
205 try:
206 files = os.listdir(kernel_dir)
207 except OSError as e:
209 if e.errno in (errno.ENOTDIR, errno.ENOENT):
210 continue
211 raise

Adding following to code could solve this issue:
if e.errno in (errno.ENOTDIR, errno.ENOENT, errno.EACCES)