Test that dodola.services.validate actually fails bad data

[brews]

We test dodola.services.validate in dodola.tests.test_services.test_validation() for the "happy path" (well-behaved data), but it would be great if we could test to ensure validation correctly catches each of the conditions that it's supposed to catch.

I think I've mentioned this in a few previous PRs, but I'm putting it here so we dont' forget.