[views] remove reference to the MAPPING_CHECKERS dict (closes #3810219)
Was removed by by the changeset 65d93a4fd11c
([multi-sources-removal] Drop pyrorql and zmqrql sources)
missing-dep-for-interpreter make => make | build-essential | dpkg-dev (usr/share/pyshared/cubicweb/skeleton/debian/rules.tmpl)