got this:
Removing installed version 4.3.18 of VirtualBox Guest Additions...
Copying additional installer modules ...
Installing additional modules ...
Removing existing VirtualBox DKMS kernel modules ...done.
Removing existing VirtualBox non-DKMS kernel modules ...done.
Building the VirtualBox Guest Additions kernel modules ...done.
Doing non-kernel setup of the Guest Additions ...done.
You should restart your guest to make sure the new modules are actually used

stdin: is not a tty
Got different reports about installed GuestAdditions version:
Virtualbox on your host claims:   4.3.18
VBoxService inside the vm claims: 5.0.26
Going on, assuming VBoxService is correct...
Got different reports about installed GuestAdditions version:
Virtualbox on your host claims:   4.3.18
VBoxService inside the vm claims: 5.0.26
Going on, assuming VBoxService is correct...
Got different reports about installed GuestAdditions version:
Virtualbox on your host claims:   4.3.18
VBoxService inside the vm claims: 5.0.26
Going on, assuming VBoxService is correct...
Restarting VM to apply changes...
Vagrant exited after cleanup due to external interrupt.