Bug summary

In a development install, running pytest -s hangs indefinitely. This causes VSCode's python test explorer to also hang indefinitely as it tries to populate the list of tests (it seems like it ignores settings.json for the command to populate the list). The behavior occurs when running a single test, e.g.

Code for reproduction

pytest -s --co lib/matplotlib/tests/test_legend.py::test_text_nohandler_warning

Actual outcome

pytest-xvfb could not find Xvfb. You can install it to prevent windows from being shown.
======================================== test session starts ========================================
platform linux -- Python 3.10.12, pytest-7.4.2, pluggy-1.3.0
rootdir: /home/xenophon/github/matplotlib
configfile: pytest.ini
plugins: xdist-3.3.1, rerunfailures-12.0, timeout-2.2.0, cov-4.1.0, xvfb-3.0.0
collecting ... 

(keeps collecting indefinitely)

Expected outcome

Detects all tests

Additional information

No response

Operating system

Linux 6.2.0-34-generic; Ubuntu 22.04.1

Matplotlib Version

dev build on current master, fcd5bb1a2b

Matplotlib Backend

agg

Python version

3.10.12

Jupyter version

N/A

Installation

None