This section has caused a lot of user confusion since PEP 517/518. It seems that users are referring to this section for advice about how to deal with build time issues, which contains statements that do not hold true for build requirements.
This example did not make sense unless it was possible to install specify a
version of a package one installs referencing by the path (here: `.`).
A new example for the local installation with an extra has been added
instead.