As a proof that fixing what's described in T1454 makes the `pip
install` instruction work.
pip-swh-packages depends on the py-depgraph script. That script is
used for the graphviz dependency schema generation. So the output
should not be changed (i think).
- order is no longer completely respected (storage always the last)
- swh-storage is hard-coded
- it works
I do not see a better way to fix it yet (ideas welcome ;).