Fix Windows compatibility with multithreading

[dolfinus]

Hi.

I've faced with some tests of Jupyterhub Notebook repo are failing:

Traceback (most recent call last):
  File "c:\hostedtoolcache\windows\python\3.6.8\x64\lib\site-packages\tornado\web.py", line 1704, in _execute
    result = await result
  File "c:\hostedtoolcache\windows\python\3.6.8\x64\lib\site-packages\tornado\gen.py", line 234, in wrapper
    yielded = ctx_run(next, result)
  File "c:\hostedtoolcache\windows\python\3.6.8\x64\lib\site-packages\tornado\gen.py", line 162, in _fake_ctx_run
    return f(*args, **kw)
  File "D:\a\notebook\notebook\notebook\services\contents\handlers.py", line 237, in delete
    yield maybe_future(cm.delete(path))
  File "D:\a\notebook\notebook\notebook\services\contents\manager.py", line 279, in delete
    self.delete_file(path)
  File "D:\a\notebook\notebook\notebook\services\contents\filemanager.py", line 533, in delete_file
    send2trash(os_path)
  File "c:\hostedtoolcache\windows\python\3.6.8\x64\lib\site-packages\send2trash\plat_win_modern.py", line 31, in send2trash
    shell.CLSID_FileOperation, None, pythoncom.CLSCTX_ALL, shell.IID_IFileOperation,
pywintypes.com_error: (-2147221008, 'CoInitialize has not been called.', None, None)

According to https://stackoverflow.com/questions/37258257/why-does-this-script-not-work-with-threading-python, it is important to call .CoInitialize() method to allow win32 API calls in multithread mode.

[arsenetar]

When I look into the information on .CoInitialize() I see that CoUninitialize() should be called for each call, this is shown in the example in the email thread: https://mail.python.org/pipermail/python-win32/2008-June/007788.html. I need to look into understanding this a bit more but that seems to be what the Microsoft COM documentation suggests as well at https://docs.microsoft.com/en-us/windows/win32/api/objbase/nf-objbase-coinitialize and https://docs.microsoft.com/en-us/windows/win32/api/combaseapi/nf-combaseapi-couninitialize.

[dolfinus]

Sorry, I've missed a notification about your comment. Thank you for merging a fix!

[dolfinus]

Could you please release a fixed version?

[arsenetar]

@dolfinus 1.8.0 is now pushed.

[dolfinus]

Thank you, tests have been passed successfully:
https://github.com/dolfinus/notebook/runs/3278236460?check_suite_focus=true