8.1.3.1 incompatible character encodings

incompatible character encodings: UTF-8 and ASCII-8BIT (Encoding::CompatibilityError)

If you receive this error when running vagrant up, even after vagrant destroy, use VirtualBox to see if the VM still exists. If so, delete it from within VirtualBox.

$ VBoxManage list vms

This can occur after deleting the project’s .vagrant sub-folder (e.g. through git clean), whilst there is still an activate Vagrant instance. Web searches suggest there are other scenarios that result in a similarly confusing error message.