Remove xfail; tests now pass on macOS. Ref #985.

testing/test_pdb.py

@@ -267,10 +267,6 @@ class TestPDB(object):
         child.read()
         self.flush(child)
 
-    # For some reason the interaction between doctest's and pytest's output
-    # capturing mechanisms are messing up the stdout on mac. (See #985).
-    # Should be solvable, but skipping until we have a chance to investigate.
-    @pytest.mark.xfail("sys.platform == 'darwin'", reason='See issue #985', run=False)
     def test_pdb_interaction_doctest(self, testdir):
         p1 = testdir.makepyfile("""
             import pytest