[migration] fix bug in `CWAttributeAddOp.revertprecommit_event`
The `rdefdef` attribute is set during the operation execution. In some the
operation crash before this assignment. In such case `revertprecommit` raise an
attribute error crashing the whole process and shadowing the original error.
This changeset detect and Avoid this situation.
#! /bin/sh -e
#
if [ "$1" = configure ]; then
if which install-docs >/dev/null 2>&1; then
install-docs -i /usr/share/doc-base/cubicweb-doc
fi
fi
#DEBHELPER#
exit 0