I'm wondering if there is a test framework that allows for tests to be declared as being dependent on other tests.  This would imply that they should not be run, or that their results should not be prominently displayed, if the tests that they depend on do not pass.
The point of such a setup would be to allow the root cause to be more readily determined in a situation where there are many test failures.
As a bonus, it would be great if there some way to use an object created with one test as a fixture for other tests.
Is this feature set provided by any of the Python testing frameworks?  Or would such an approach be antithetical to unit testing's underlying philosophy?
The test runners py.test, Nosetests and unit2/unittest2 all support the notion of "exiting after the first failure".  py.test more generally allows to specify "--maxfail=NUM" to stop running and reporting after NUM failures. This may already help your case especially since maintaining and updating dependencies for tests may not be that interesting a task.
Test framework allowing tests to depend on other tests