I forgot to mention: please make sure to have exactly three commits: the first one should add yourself as a maintainer and the two others are for the two packages.

The package itself seems fine now, I have two questions though:

• nix-build -A pythonPackages.notedown works fine, but python.withPackages (ps: with ps; [ notedown ]) fails with the following error:

  these derivations will be built:
    /nix/store/slgls8y80s9v69pny5dv372zjdva298b-python-2.7.15-env.drv
  building '/nix/store/slgls8y80s9v69pny5dv372zjdva298b-python-2.7.15-env.drv'...
  collision between `/nix/store/4hi6nipj7x4kml0cl0lg1p5giw13ym1f-python2.7-backports.shutil_get_terminal_size-unstable-2016-02-21/lib/python2.7/site-packages/backports/__init__.pyc' and `/nix/store/bibs4wix1jlnj29b6b49ac4wvfmc22m0-python2.7-configparser-3.5.0/lib/python2.7/site-packages/backports/__init__.pyc'
  builder for '/nix/store/slgls8y80s9v69pny5dv372zjdva298b-python-2.7.15-env.drv' failed with exit code 25
  error: build of '/nix/store/slgls8y80s9v69pny5dv372zjdva298b-python-2.7.15-env.drv' failed
  

• When importing notedown in a python3 environment I get the following warning (the module works perfectly fine):

  >>> import notedown
  /nix/store/1aagq246as0xvnphsw858r5lpgcv645r-python3-3.7.2-env/lib/python3.7/site-packages/IPython/html.py:14: ShimWarning: The `IPython.html` package has been deprecated since IPython 4.0. You should import from `notebook` instead. `IPython.html.widgets` has moved to `ipywidgets`.
    "`IPython.html.widgets` has moved to `ipywidgets`.", ShimWarning)
  

  I assume this is just because of a dependency of notedown, right? Or is that fixable here as well?

@Ma27 Warning is removed after adding notebook to propagated build inputs. I don't know why withPackages approach is causing collisions for python 2.7.

Are there any updates on this pull request, please?