Remove deprecated PolyBase from np.polynomial.polyutils

[rossbar]

np.polynomial.polyutils defines a PolyBase class that, according to the source, was deprecated back in v1.9.0:

numpy/numpy/polynomial/polyutils.py

Lines 81 to 91 in acba244

	class PolyBase:
	"""
	Base class for all polynomial types.
	Deprecated in numpy 1.9.0, use the abstract
	ABCPolyBase class instead. Note that the latter
	requires a number of virtual functions to be
	implemented.
	"""
	pass

I am wondering if it can be removed from the code base. v1.9 was quite some time ago, though I'm not sure this proposal is in line with whatever the official deprecation policy is. For what it's worth, PolyBase does not appear to be used within the numpy code base anymore, so the question is whether downstream libraries have had sufficient time (and notification) to remove PolyBase from their codebases.

[seberg]

Would be OK to try I think. We could also use the module __getattr__ to deprecate the name itself for now and wait until 3.7 is a required dependency. Its very slow, but probably not much of an issue, and I assume we need the module __getattr__ for other polynomial cleanup soon in any case.

[rossbar]

The getattr idea is an interesting one. We'll see if there are other names in the polynomial/poly1d cleanup that could benefit from this.

[BvB93]

Another option would be to add a PolyBase.__init_subclass__ method that issues a warning upon subclassing.

[charris]

to remove PolyBase from their codebases.

I thought it unlikely anyone was using it at the time, but played it safe. It can probably be removed without causing problems.

[hollycorbett]

I can pick up this one

[charris]

Closing as completed.