Run functional tests against LibVNCServer examples

[sibson]

Summary

• add helpers to build LibVNCServer example binaries and expose vncdotool CLIs without installation
• update functional tests to launch the real example servers and vncdotool entry points instead of skipping
• ensure the LibVNCServer makefile builds the example server used by screen capture tests

Testing

• PYTHONPATH=. python -m unittest discover -t . -s tests/functional

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https://chatgpt.com/codex/tasks/task_e_6906dc28027c8327a29ada194f314ccf

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Edit (2026-06-16): Corrected the Testing command. The original pytest tests/functional -q happened to work under pytest, but unittest discover tests/functional (and make test-func) failed with "attempted relative import with no known parent package" — see #326. Running discovery with -t . keeps the tests.functional package context.

[pmhahn]

This fails for me:

$ PYTHONPATH=. pytest-3 tests/functional -q

======================================================================================== ERRORS ========================================================================================
____________________________________________________________________ ERROR collecting tests/functional/test_xvnc.py ____________________________________________________________________
ImportError while importing test module '…/vncdotool/tests/functional/test_xvnc.py'.
Hint: make sure your test modules/packages have valid Python names.
Traceback:
/usr/lib/python3.12/importlib/__init__.py:90: in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
tests/functional/test_xvnc.py:5: in <module>
    from pyvirtualdisplay import Display
E   ModuleNotFoundError: No module named 'pyvirtualdisplay'
=============================================================================== short test summary info ================================================================================
ERROR tests/functional/test_xvnc.py

Maybe also add pytest to requirements-dev.txt?

Also the way documented in DEVELOP.rst does not work:

$ make test-func
python3 -m unittest discover  tests/functional
EEE
======================================================================
ERROR: test_proxy (unittest.loader._FailedTest.test_proxy)
----------------------------------------------------------------------
ImportError: Failed to import test module: test_proxy
Traceback (most recent call last):
  File "…/lib/python3.13/unittest/loader.py", line 396, in _find_test_path
    module = self._get_module_from_name(name)
  File "…/lib/python3.13/unittest/loader.py", line 339, in _get_module_from_name
    __import__(name)
    ~~~~~~~~~~^^^^^^
  File "…/tests/functional/test_proxy.py", line 9, in <module>
    from .cli import spawn_command
ImportError: attempted relative import with no known parent package