In an attempt to fix iPython functionalities of Gajim, I applied the patch used in the Accerciser project: https://gitlab.gnome.org/GNOME/accerciser/commit/3008be6e0cbf6d42b55354405b37693b5c4c62c6

I also took the opportunity to take some other portions of the code used by Accerciser to avoid further tracebacks. I added a check for IPython in gui_interface.py , so we can abort early if IPython is not installed. Additionally, some code-cleanup was done.

Installed iPython version: 7.5.0

Usage is described here: https://dev.gajim.org/gajim/gajim/wikis/development/IPythonEmbeddedShell

Fixes #9652 (closed) and #9195 (closed)