mark test_comments as xfail on pypy

while migrating this code it was noticed that this test was failing even
on the original py repository, so it was decided to xfail it and investigate
later

testing/code/test_source.py

@@ -506,6 +506,8 @@ def test_oneline_and_comment():
     source = getstatement(0, "raise ValueError\n#hello")
     assert str(source) == "raise ValueError"
 
+@pytest.mark.xfail(hasattr(sys, "pypy_version_info"),
+                   reason='does not work on pypy')
 def test_comments():
     source = '''def test():
     "comment 1"