Hi all,

Here is my proposed correction for the breakage I introduced when I
updated python-prompt-toolkit (bugs #41738, #41729 and 41730).

As you can see on the attached images, I disconnected all packages that
depend on ppt2 from the packages that depend on ppt3.
This should fix all reported problems. If it does not, this means that
there is an undeclared dependency, which is a bug. Please do not
hesitate to tell me about any problem you encounter that my be tied to
this change.

jupyter's &co dependency on ppt2 is still a mystery to me. It is computed
by the setuptools when they run but nowhere in the source of the
packages that have an explicit dependency on ppt2 was I able to find any
reference to it.

I have no idea how setuptools comes to the conclusion that it needs
"prompt_toolkit<2.1.0,>=2.0.0". I (grep -r -i)-ed, in the source code of
ipywidgets and could not find anything. This is black magic to me.

I would have loved to bring all those packages to ppt3 and forget about
ppt2 altogether, but because nowhere in the source is the dependency
written, I can't do it. Any help would be appreciated. In the meantime
this fix should do the trick.

I did not repair packages that were broken for reasons unrelated to
ppt, but I'm quite confident that once their brokenness is fixed, ppt3
won't be a problem for them. For example in my dirty work tree I have a
fix for python-rpy2, but it is tied to a pandas upgrade, and too many
packages depend on pandas for me to handle right now.

Cheers,

Edouard.