[datafeed] also catch EnvironmentError when trying to load the cwclientlib config file means the config file has not been found, so fall back to the old implementation instead of crashing.

usr/bin/cubicweb-ctl usr/bin/
usr/lib/PY_VERSION/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl