Testslide runner not playing well with unittest.subtests

```
In [1]: from unittest import TestCase

In [2]: class Repro(TestCase):
...: def test_repro(self):
...: for x in range(0,10):
...: with self.subTest(f"{x}") as st:
...: if x == 5:
...: raise unittest.SkipTest("skipped")
...: self.assertTrue(True)

```

testslide runner marks the entire testclass skipped.