cartesian product of algebra has troubles with base_ring #19225
Description
sage: cartesian_product((QQ['z'],))
Traceback (most recent call last)
...
/local/dakrenn/sage/6.9.beta6/local/lib/python2.7/site-packages/sage/categories/unital_algebras.pyc in __init_extra__(self)
--> 107 H = Hom(base_ring, self, Rings()) # TODO: non associative ring!
...
AttributeError: 'NoneType' object has no attribute '_is_category_initialized'
Depends on #29225
CC: @roed314 @behackl @pjbruin @nthiery
Component: coercion
Author: Peter Bruin
Branch: dcc25ea
Reviewer: Travis Scrimshaw
Issue created by migration from https://trac.sagemath.org/ticket/19225