Uninstalling old VirtualBox DKMS kernel modules ...done.
Trying to register the VirtualBox kernel modules using DKMSError! Bad return status for module build on kernel: 4.9.0-0.bpo.4-amd
64 (x86_64)
Consult /var/lib/dkms/vboxhost/4.3.40/build/make.log for more information.
...failed!
(Failed, trying without DKMS)
Recompiling VirtualBox kernel modules ...failed!
(Look at /var/log/vbox-install.log to find out what went wrong)