Require jupyter-packaging as setup deps

[fcollonval]

Fixes #159
Fixes #167

The data files should not be conditionned on anything => jupyter packaging needs to be installed as setup dependencies.

[fcollonval]

The real problem is the command jupyter labextension develop . --overwrite

It raises:

Traceback (most recent call last):
  File "setup.py", line 17, in <module>
    raise e
  File "setup.py", line 9, in <module>
    from jupyter_packaging import get_data_files, npm_builder, wrap_installers
ModuleNotFoundError: No module named 'jupyter_packaging'
An error occured.
FileNotFoundError: The Python package `.` is not a valid package, it is missing the `setup.py` file.

as it calls command such python setup.py --name. So I think we need either jupyterlab to require jupyter-packaging or to mock it to succeed at handling the labextension develop.

@blink1073 @jtpio @krassowski what do you think?

[ktaletsk]

I would like to add that current changes in this PR also fix another issue for me: when trying to manually build python source archive and a wheel with python setup.py sdist bdist_wheel and then install from the wheel (pip install myextension-0.1.0-py3-none-any.whl) server- and labextensions are not getting installed.

On 3.0, this manual build process gives:

$ jupyter server extension list
Config dir: /home/jovyan/.jupyter

Config dir: /opt/conda/etc/jupyter
    jupyterlab enabled
    - Validating jupyterlab...
      jupyterlab 3.0.16 OK
    nbclassic enabled
    - Validating nbclassic...
      nbclassic  OK

Config dir: /usr/local/etc/jupyter

$ jupyter labextension list
JupyterLab v3.0.16

and on the fix/setup_py:

$ jupyter server extension list
Config dir: /home/jovyan/.jupyter

Config dir: /opt/conda/etc/jupyter
    jupyterlab enabled
    - Validating jupyterlab...
      jupyterlab 3.0.16 OK
    myextension enabled
    - Validating myextension...
      myextension 0.1.0 OK
    nbclassic enabled
    - Validating nbclassic...
      nbclassic  OK

Config dir: /usr/local/etc/jupyter

$ jupyter labextension list
JupyterLab v3.0.16
/opt/conda/share/jupyter/labextensions
        myextension v0.1.0 enabled OK (python, myextension)

[fcollonval]

Here is a new version that raises an error when jupyter-packaging except when introspecting package name or version (what is used by some jupyter lab build commands).

I used logging to print the warning on stderr. So it is not blocking introspection that is catching stdout.

[blink1073]

LGTM, thank you!

[fcollonval]

@ktaletsk @mlucool would you mind testing the latest version to check that it solves your issues?

[ktaletsk]

@fcollonval I confirm that it solves my issue, thank you for solving it!

[mlucool]

This works great - thanks!