Cell containerization fails because of GitHub API change

[gpelouze]

Containerization is partly broken on v2.5.0.

When containerizing a cell with a new name, we get this error:

Traceback (most recent call last):
  File "/venv/lib/python3.11/site-packages/tornado/web.py", line 1790, in _execute
    result = await result
             ^^^^^^^^^^^^
  File "/venv/lib/python3.11/site-packages/jupyterlab_vre/component_containerizer/handlers.py", line 430, in post
    do_dispatch_github_workflow, image_version = create_or_update_cell_in_repository(
                                                 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/venv/lib/python3.11/site-packages/jupyterlab_vre/component_containerizer/handlers.py", line 486, in create_or_update_cell_in_repository
    remote_hash = repository.get_contents(path=task_name + '/' + f_name).sha
                  ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/venv/lib/python3.11/site-packages/github/Repository.py", line 2137, in get_contents
    headers, data = self._requester.requestJsonAndCheck(
                    ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/venv/lib/python3.11/site-packages/github/Requester.py", line 537, in requestJsonAndCheck
    return self.__check(*self.requestJson(verb, url, parameters, headers, input, self.__customConnection(url)))
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/venv/lib/python3.11/site-packages/github/Requester.py", line 598, in __check
    raise self.createException(status, responseHeaders, data)
github.GithubException.GithubException: 404 {"message": "No object found for the path a-completely-new-cell-name-gabriel-pelouze-lifewatch-eu/task.py", "documentation_url": "https://docs.github.com/v3/repos/contents/", "status": "404"}

[gpelouze]

This is a PyGithub issue following a GitHub API change: PyGithub/PyGithub#3179