bug: python exception module name and class name both don't match

[trim21]

Describe the bug

op.read("non-exists-path") will throw exception like this:

Traceback (most recent call last):
  File "C:\Users\Trim21\proj\test\f.py", line 13, in <module>
    op.read("non-exists-path")
opendal.NotFoundError: NotFound (permanent) at stat, context: { service: redis, path: non-exists-path } => kv doesn't have this path

But if you actually try to catch exception opendal.NotFoundError you will encounter another error:

try:
    op.read("non-exists-path")
except opendal.NotFoundError as e:
    print(e)

Traceback (most recent call last):
  File "C:\Users\Trim21\proj\test\f.py", line 14, in <module>
    op.read("non-exists-path")
opendal.NotFoundError: NotFound (permanent) at stat, context: { service: redis, path: non-exists-path } => kv doesn't have this path

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "C:\Users\Trim21\proj\test\f.py", line 15, in <module>
    except opendal.NotFoundError as e:
AttributeError: module 'opendal' has no attribute 'NotFoundError'

what actually work, which is not opendal nor NotFoundError, but opendal.exceptions.NotFound :

try:
    op.read("non-exists-path")
except opendal.exceptions.NotFound as e:
    print(e)

Steps to Reproduce

import opendal


op = opendal.Operator(...)    

try:
    op.read("non-exists-path")
except opendal.NotFoundError as e:
    print(e)

Expected Behavior

exception module name should match or re-export them from top level

Additional Context

No response

Are you willing to submit a PR to fix this bug?

• Yes, I would like to submit a PR.