"""A base class for handling installable artifacts.
The requirements for anything installable are as follows:
- we must be able to determine the requirement name
(or we can't correctly handle the non-upgrade case).
- for packages with setup requirements, we must also be able
to determine their requirements without installing additional
packages (for the same reason as run-time dependencies)
- we must be able to create a Distribution object exposing the
above metadata.
- if we need to do work in the build tracker, we must be able to generate a unique
string to identify the requirement in the build tracker.
"""
=
"""A string that uniquely identifies this requirement to the build tracker.
If None, then this dist has no work to do in the build tracker, and
``.prepare_distribution_metadata()`` will not be called."""