importflaskapp=flask.Flask(__name__)deftest():pass

$pytest t.py============================= test session starts ==============================platform linux -- Python 3.6.7, pytest-5.0.0, py-1.8.0, pluggy-0.12.0rootdir: /tmp/xcollected 0 items / 1 errors==================================== ERRORS ====================================____________________________ ERROR collecting t.py _____________________________t.py:3: in <module>    app = flask.Flask(__name__)venv/lib/python3.6/site-packages/flask/app.py:381: in __init__    instance_path = self.auto_find_instance_path()venv/lib/python3.6/site-packages/flask/app.py:678: in auto_find_instance_path    prefix, package_path = find_package(self.import_name)venv/lib/python3.6/site-packages/flask/helpers.py:826: in find_package    loader, root_mod_name):venv/lib/python3.6/site-packages/flask/helpers.py:789: in _matching_loader_thinks_module_is_package    loader.__class__.__name__)E   AttributeError: AssertionRewritingHook.is_package() method is missing but is required by Flask of PEP 302 import hooks.  If you do not use import hooks and you encounter this error please file a bug against Flask.!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!=========================== 1 error in 0.31 seconds ============================

$pip freeze --allatomicwrites==1.3.0attrs==19.1.0Click==7.0Flask==1.0.3importlib-metadata==0.18itsdangerous==1.1.0Jinja2==2.10.1MarkupSafe==1.1.1more-itertools==7.1.0packaging==19.0pip==19.1.1pluggy==0.12.0py==1.8.0pyparsing==2.4.0pytest==5.0.0setuptools==41.0.1six==1.12.0wcwidth==0.1.7Werkzeug==0.15.4wheel==0.33.4zipp==0.5.1