Improve test runner status rendering

[aljazerzen]

Fix of test runner status rendering which would sometimes display this:

It can be reproduced by such tests:

    def test_debug_with_really_long_names_fast_1(self):
        import time
        time.sleep(1)
    def test_debug_with_really_long_names_fast_2(self):
        import time
        time.sleep(1)
    def test_debug_with_really_long_names_fast_3(self):
        import time
        time.sleep(1)
    def test_debug_with_really_long_names_fast_4(self):
        import time
        time.sleep(1)
    def test_debug_with_really_long_names_fast_5(self):
        import time
        time.sleep(1)
    def test_debug_with_really_long_names_fast_6(self):
        import time
        time.sleep(1)
    def test_debug_with_really_long_names_slow_1(self):
        import time
        time.sleep(5)