"PR / guitest / run" doesn't work

[drew2a]

https://github.com/Tribler/tribler/runs/7334057865?check_suite_focus=true#step:5:47

As far as I know this issue appeared about one week ago, and it is not related to a particular GUI test.

src/tribler/gui/tests/test_util.py::test_quote_plus_unicode_compound PASSED [ 60%]
src/tribler/gui/tests/test_gui.py::test_feedback_dialog_report_sent Fatal Python error: Aborted
Current thread 0x00007fa8ab035740 (most recent call first):
  File "/home/runner/work/tribler/tribler/src/tribler/gui/single_application.py", line 28 in __init__
  File "/home/runner/work/tribler/tribler/src/tribler/gui/tribler_app.py", line 27 in __init__
  File "/home/runner/work/tribler/tribler/src/tribler/gui/tests/test_gui.py", line 40 in fixture_window
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/fixtures.py", line 883 in call_fixture_func
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/fixtures.py", line 1111 in pytest_fixture_setup
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_callers.py", line 39 in _multicall
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_manager.py", line 80 in _hookexec
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_hooks.py", line 265 in __call__
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/fixtures.py", line 1057 in execute
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/fixtures.py", line 659 in _compute_fixture_value
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/fixtures.py", line 573 in _get_active_fixturedef
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/fixtures.py", line 554 in getfixturevalue
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/fixtures.py", line 541 in _fillfixtures
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/python.py", line 1764 in setup
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 491 in setup
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 154 in pytest_runtest_setup
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_callers.py", line 39 in _multicall
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_manager.py", line 80 in _hookexec
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_hooks.py", line 265 in __call__
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 259 in <lambda>
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 338 in from_call
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 258 in call_runtest_hook
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 219 in call_and_report
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 124 in runtestprotocol
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/runner.py", line 111 in pytest_runtest_protocol
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_callers.py", line 39 in _multicall
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_manager.py", line 80 in _hookexec
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_hooks.py", line 265 in __call__
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/main.py", line 3[47](https://github.com/Tribler/tribler/runs/7334057865?check_suite_focus=true#step:5:48) in pytest_runtestloop
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_callers.py", line 39 in _multicall
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_manager.py", line 80 in _hookexec
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_hooks.py", line 265 in __call__
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/main.py", line 322 in _main
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/main.py", line 268 in wrap_session
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/main.py", line 315 in pytest_cmdline_main
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_callers.py", line 39 in _multicall
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_manager.py", line 80 in _hookexec
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/pluggy/_hooks.py", line 265 in __call__
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/config/__init__.py", line 1[64](https://github.com/Tribler/tribler/runs/7334057865?check_suite_focus=true#step:5:65) in main
  File "/home/runner/.virtualenvs/.venv/lib/python3.8/site-packages/_pytest/config/__init__.py", line 1[87](https://github.com/Tribler/tribler/runs/7334057865?check_suite_focus=true#step:5:88) in console_main
  File "/home/runner/.virtualenvs/.venv/bin/pytest", line 8 in <module>
Aborted (core dumped)

Appeared: #6969, #6966