No, because the rich comparison docs explicitly state that the
interpreter makes no assumptions about the relationship between != and
== (or, more precisely, __eq__ and __ne__).

"""There are no implied relationships among the comparison operators.
The truth of x==y does not imply that x!=y is false. """

(from http://docs.python.org/reference/datamodel.html#basic-customization)

If someone is writing unit tests for comparison methods they should
explicitly test all 6 operations.