capsys.disabled() not working as expected

gistfile1.txt

___________________________ TestXXX.test_xxx ___________________________
...

    def test_csv(self, app, client, basic_user, bulk_add_test_data, capsys):
        print(app.show_routes(rule_pattern=r'/api2/xxx/.*'))
        response = client.get(
            flask.url_for(
                'xxx',
            ),
            headers=guard.pack_header_for_user(basic_user),
        )
    
        with capsys.disabled():
            import ipdb
>           ipdb.set_trace()

test/api/xxx.py:89: 
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 
../../.pyenv/versions/3.6.5/lib/python3.6/contextlib.py:85: in __exit__
    def __exit__(self, type, value, traceback):
../../.pyenv/versions/3.6.5/lib/python3.6/bdb.py:53: in trace_dispatch
    return self.dispatch_call(frame, arg)
../../.pyenv/versions/3.6.5/lib/python3.6/bdb.py:85: in dispatch_call
    self.user_call(frame, arg)
../../.pyenv/versions/3.6.5/lib/python3.6/pdb.py:251: in user_call
    self.interaction(frame, None)
../../.local/share/virtualenvs/cem-data-bYY-kAuC/lib/python3.6/site-packages/IPython/core/debugger.py:297: in interaction
    OldPdb.interaction(self, frame, traceback)
../../.pyenv/versions/3.6.5/lib/python3.6/pdb.py:352: in interaction
    self._cmdloop()
../../.pyenv/versions/3.6.5/lib/python3.6/pdb.py:321: in _cmdloop
    self.cmdloop()
../../.pyenv/versions/3.6.5/lib/python3.6/cmd.py:126: in cmdloop
    line = input(self.prompt)
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ 

self = <_pytest.capture.DontReadFromInput object at 0x7ff4a2e9a518>, args = ()

    def read(self, *args):
>       raise IOError("reading from stdin while output is captured")
E       OSError: reading from stdin while output is captured

../../.local/share/virtualenvs/cem-data-bYY-kAuC/lib/python3.6/site-packages/_pytest/capture.py:653: OSError
----------------------------- Captured stdout call -----------------------------
[
  [ 'rule',                       'methods',           'endpoint',              ],
  [ '/api2/xxx/csv',              'GET,HEAD,OPTIONS',  'xxx.csv',               ],
  [ '/api2/xxx/merge',            'POST,OPTIONS',      'xxx.merge',             ],
]
---------------------------- Captured logging call -----------------------------
[  INFO   ] REQUEST -> /api2/xxx/csv [GET] ()
================ 1 failed, 1 warnings, 1 error in 3.60 seconds =================
Exception ignored in: <generator object disabled at 0x7ff48f6d19e8>
Traceback (most recent call last):
  File "/home/xxx/.local/share/virtualenvs/xxx-bYY-kAuC/lib/python3.6/site-packages/_pytest/capture.py", line 380, in disabled
  File "/home/xxx/.pyenv/versions/3.6.5/lib/python3.6/contextlib.py", line 99, in __exit__
  File "/home/xxx/.local/share/virtualenvs/cem-data-bYY-kAuC/lib/python3.6/site-packages/_pytest/capture.py", line 167, in global_and_fixture_disabled
  File "/home/xxx/.local/share/virtualenvs/cem-data-bYY-kAuC/lib/python3.6/site-packages/_pytest/capture.py", line 120, in resume_global_capture
AttributeError: 'NoneType' object has no attribute 'resume_capturing'