When specifying "http_interface" with the packer provider, and not specifying any "http_bind_address", it results in the error:

either http_interface of http_bind_address can be specified

Expected behavior:

1. Error message should say "or" instead of "of" if these options are actually mutually exclusive
2. When only http_interface is specified in the configuration, this error message does not appear, but it just obtains the IP address from the specified interface

Workaround: use http_bind_address instead of http_interface. I would prefer http_interface was functional, however this is getting me by for now.