This prevents conflicting variants of python-prompt-toolkit from being
installed, which prevented jupyter from being installed.
* gnu/packages/python-xyz.scm (python-ipython)[propagated-inputs]: Replace
python-prompt-toolkit with python-prompt-toolkit-2.
(python-widgetsnbextension)[propagated-inputs]: Do not use
prompt-toolkit-2-instead-of-prompt-toolkit on python-ipykernel.
(python-ipywidgets)[propagated-inputs]: Do not use
prompt-toolkit-2-instead-of-prompt-toolkit on python-ipython.
(python-jupyter-console)[propagated-inputs]: Do not use
prompt-toolkit-2-instead-of-prompt-toolkit on python-ipykernel.
(prompt-toolkit-2-instead-of-prompt-toolkit): Remove variable.
* gnu/packages/machine-learning.scm (python-iml)[propagated-inputs]: Do not
use prompt-toolkit-2-instead-of-prompt-toolkit on python-ipython.
7146c8c75d