BUG: SDF frontend breaks load() if target file lacks read permission

[Xarthisius]

Bug report

Bug summary

While trying to yt.load() a file without permission SDF._is_valid() yields PermissionError and breaks the detection loop. If we want to check permission in yt.load() itself that'd be fine, but no frontend should die cause of it.

Code for reproduction

(root) $ echo "hello world!" > /tmp/hello.txt
(root) $ chmod og-r /tmp/hello.txt
(user) $ python -c 'import yt; yt.load("/tmp/hello.txt")'

Actual outcome

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/xarth/codes/xarthisius/yt/yt/_maintenance/deprecation.py", line 73, in inner
    return func(*args, **kwargs)
  File "/home/xarth/codes/xarthisius/yt/yt/loaders.py", line 112, in load
    if cls._is_valid(fn, *args, **kwargs):
  File "/home/xarth/codes/xarthisius/yt/yt/frontends/sdf/data_structures.py", line 186, in _is_valid
    with open(sdf_header, encoding="ISO-8859-1") as f:
PermissionError: [Errno 13] Permission denied: '/tmp/hello.txt'

Expected outcome

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/home/xarth/codes/xarthisius/yt/yt/_maintenance/deprecation.py", line 73, in inner
    return func(*args, **kwargs)
  File "/home/xarth/codes/xarthisius/yt/yt/loaders.py", line 124, in load
    raise YTUnidentifiedDataType(fn, *args, **kwargs)
yt.utilities.exceptions.YTUnidentifiedDataType: Could not determine input format from '/tmp/hello.txt'

or yt.load raising PermissionError

Version Information

• Operating System: Ubuntu 20.04
• Python Version: 3.9
• yt version: last_yt3-7052-gaf4dbf6b1

[neutrinoceros]

I suspect SDF may just be the first one that dies on this, but it's likely that other frontends have the same issue.

[matthewturk]

Can we catch PermissionError early on and fail globally?

[neutrinoceros]

This was fixed in #4285