9. Add HurwitzMatrixAlgebra subclass between MatrixAlgebra and
OctonionMatrixAlgebra.
+
+10. Every once in a long while, the test
+
+ sage: set_random_seed()
+ sage: x = random_eja().random_element()
+ sage: x.is_invertible() == (x.det() != 0)
+
+ in eja_element.py returns False.