I don't believe there is currently a way to print only the list of tests which failed.

--report_level=short only prints the numbers of passed and failing tests
--report_level=detailed prints a very verbose list of all tests

Is there a middle ground which will give me the names of tests which have failed, but not those which have passed?

Something along the lines of:

Test module "Master Test Suite" has failed with:
  1 test case out of 9 failed
  1 test case out of 9 aborted
  1 assertion out of 30 failed

  Test case "foo_test" was aborted with:
    1 assertion out of 1 failed

TIA
Steve