no_installation_outside_venv

There is no (known) use case for protoprimer to be installed outside a venv.

In fact, the entire bootstrap process with all states imply venv usage.

Allowing it to be installed outside venv would also lead to come complications of detecting leap_primer configuration (see conf_leap) - its location is assumed to be in the same directory with stand-alone proto_code (not in the package installation directory).