A VirtualBox machine with the name 'vm_name' already exists. Please use another name or delete the machine with the existing name, and try again.
I listed current running virtual machines from the command line :
vboxmanage list vms
Then proceeded with the removal of the offending virtual machine :
VBoxManage unregistervm 8ba467b7-da96-4f68-9bf8-671dd6f0d007 --delete
vagrant up --provision