[dataimport] fix ucsvreader for python3 The csv module in python3 wants str, so use a StreamReader to feed csv.reader and don't decode the output

usr/bin/cubicweb-ctl usr/bin/
usr/lib/python2*/*-packages/cubicweb/cwctl.py
../cubicweb-ctl.bash_completion etc/bash_completion.d/cubicweb-ctl