[migractions] add sanity check in rename_relation_type
If the relation is still present in the fs schema, we probably shouldn't
be renaming it (because it's still in use somewhere, possibly in a
different cube). Closes #3608172
missing-dep-for-interpreter make => make | build-essential | dpkg-dev (usr/share/pyshared/cubicweb/skeleton/debian/rules.tmpl)