Competing ExceptionInfo classes. Losing stacktraces in terminal output

[Magicjarvis]

There are two ExceptionInfo classes and one of them seems to be eating exception stacktraces. any ideas?
one lives here venv/src/py/py/_code/code.py (I've added a print to its init and called it "ExceptionInfo #1"
and the other lives here /venv/lib/python3.5/site-packages/py/_code/code.py (ExceptionInfo #2)

Minimal example
Given this test file
test_repro.py

def really_do_the_assert():
    assert 1 == 0

def test_repro():
    really_do_the_assert()

class TestFoo(unittest.TestCase):
    def test_ugh(self):
        assert 1 == 0

I get this result from pytest test/test_repro.py

collected 2 items

test/test_repro.py ExceptionInfo #1 tup=None, exprinfo=None
FF
===Flaky Test Report===


===End Flaky Test Report===

============================================== FAILURES ==============================================
_____________________________________________ test_repro _____________________________________________
/Users/jarvis/webdev/py/example_repo/test/test_repro.py:5: AssertionError: assert 1 == 0
__________________________________________ TestFoo.test_ugh __________________________________________

self = <test.test_repro.TestFoo testMethod=test_ugh>

    def test_ugh(self):
>       assert 1 == 0
E       AssertionError: assert 1 == 0

test/test_repro.py:15: AssertionError
---------------------------------------- Captured stdout call ----------------------------------------
ExceptionInfo #2 tup=(<class 'AssertionError'>, AssertionError('assert 1 == 0',), <traceback object at 0x109ea8888>), exprinfo=None
====================================== 2 failed in 4.75 seconds ======================================
(venv) ➜  example_repo git:(test-repro) ✗

pytest version 3.0.7; mac os x

The ExceptionInfo used for test_repro() doesn't have an exception tuple associated, which is why i assume it can't print the stacktrace. Any ideas what's up?