PEP 517 specifies a standard API for systems which build Python
packages.

PEP 660 extends it with a build mode that leads to editable installs.

This package contains wrappers around the hooks specified by PEP 517
and PEP 660. It provides:

- A mechanism to call the hooks in a subprocess, so they are isolated
  from the current process.
- Fallbacks for the optional hooks, so that frontends can call the
  hooks without checking which are defined.
