To reproduce the issue:

* compile Python 3.6 in debug mode
* download https://pypi.python.org/pypi/SQLAlchemy/1.1.0b3
* Then type:
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./python -m venv venvsqla
cd venvsqla
source bin/activate
python -m pip install pytest 

tar -xf ../SQLAlchemy-1.1.0b3.tar.gz 
cd SQLAlchemy-1.1.0b3/
python setup.py install 
python -X faulthandler -m pytest test/aaa_profiling/test_compiler.py -v -s
---

I get:
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================================================ test session starts ================================================
platform linux -- Python 3.7.0a0, pytest-3.0.2, py-1.4.31, pluggy-0.3.1 -- /home/haypo/prog/python/default/venvsqla/bin/python
cachedir: .cache
rootdir: /home/haypo/prog/python/default/venvsqla/SQLAlchemy-1.1.0b3, inifile: setup.cfg
collecting 0 itemspython: Objects/dictobject.c:1739: _PyDict_Pop: Assertion `ix >= 0' failed.
Fatal Python error: Aborted

Current thread 0x00007f6d909da700 (most recent call first):
  File "/home/haypo/prog/python/default/venvsqla/SQLAlchemy-1.1.0b3/test/../lib/sqlalchemy/util/langhelpers.py", line 796 in expire_instance
  File "/home/haypo/prog/python/default/venvsqla/SQLAlchemy-1.1.0b3/test/../lib/sqlalchemy/sql/selectable.py", line 666 in _reset_exported
  File "/home/haypo/prog/python/default/venvsqla/SQLAlchemy-1.1.0b3/test/../lib/sqlalchemy/sql/selectable.py", line 1908 in _generate
  File "/home/haypo/prog/python/default/venvsqla/SQLAlchemy-1.1.0b3/test/../lib/sqlalchemy/sql/base.py", line 44 in _generative
  File "<string>", line 2 in apply_labels
  File "/home/haypo/prog/python/default/venvsqla/SQLAlchemy-1.1.0b3/test/aaa_profiling/test_compiler.py", line 12 in <module>
  File "/home/haypo/prog/python/default/venvsqla/lib/python3.7/site-packages/_pytest/assertion/rewrite.py", line 207 in load_module
  File "<frozen importlib._bootstrap>", line 616 in _load_backward_compatible
  File "<frozen importlib._bootstrap>", line 646 in _load_unlocked
  File "<frozen importlib._bootstrap>", line 950 in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 961 in _find_and_load
  File "/home/haypo/prog/python/default/venvsqla/lib/python3.7/site-packages/py/_path/local.py", line 650 in pyimport
  File "/home/haypo/prog/python/default/venvsqla/lib/python3.7/site-packages/_pytest/python.py", line 411 in _importtestmodule
...
---