/usr/src/openvswitch-1.4.0/debian/openvswitch-datapath-dkms.prerm is in openvswitch-datapath-dkms 1.4.0-1ubuntu1.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 | #!/bin/sh
set -e
package=openvswitch-datapath-dkms
name=openvswitch
version=`dpkg-query -W -f='${Version}' "$package" \
|rev|cut -d- -f2-|rev|cut -d':' -f2|tr -d "\n"`
dkms remove -m "$name" -v "$version" --all || true
#DEBHELPER#
exit 0
|