Before installing dependencies run a check for the python-dev-is-python3 package and only install it if found (otherwise use python-dev). This allows older versions of debian (and derivatives) to properly install the defined dependencies.
Vagrant Core Plugins
These are plugins that ship with Vagrant. Vagrant core uses its own plugin system to power a lot of the core pieces that ship with Vagrant. Each plugin will have its own README which explains its specific role.
Generate proto
grpc_tools_ruby_protoc -I . --ruby_out=gen/plugin --grpc_out=gen/plugin ./plugin_server.proto