Make provenance mandatory in `Loader.get_loader()`
We had one offender breaking this rule, which is the _includes.py
which wraps it's own custom errors instead of providing the precious provenance information to the Loader
when asking it for a child Loader
.
Changed the signature of Loader.get_loader()
to make provenance
a positional argument with no default value, ensuring nobody can call this function without providing a providence argument.