code: def dependency_failed(self, test):
          
          for d in (self.test_name(i) for i in dependencies[test]):
              if d in (self.test_name(str(t[0])) for t in self.results.failures):
                  return "Required test '{}' FAILED".format(d)
              if d in (self.test_name(str(t[0])) for t in self.results.errors):
                  return "Required test '{}' ERRORED".format(d)
              if d in (self.test_name(str(t[0])) for t in self.results.skipped):
                  return "Required test '{}' SKIPPED".format(d)
          return None
docs: Returns an error string if any of the dependencies failed