Bug#944227: breaks

[Gordon Ball <gordon@chronitis.net>]

I've added Breaks to the package in git:

aws-shell (<= 0.2.1) [1]
mycli (<< 1.19)
pgcli (<< 2)
python3-ipython (<< 7)
python3-jupyter-console (<< 6)
python3-softlayer (<< 5.8)

[1] No upstream version which fixes this, but I assume adding an
unversioned Breaks: is a bad idea.

I think that having heard from sagemath, pgcli and mycli, the only
outstanding blockers are aws-shell (#944542) and possibly
mlbstreamer (#944545).

For my part (ipython, jupyter-console) I'm waiting for python-backcall
and ipython-py2 to go through NEW before ipython can be upgraded.