test_grab_x11 failure when no X session is running

<!-- Thank you for reporting an issue. Follow these guidelines to ensure your issue is handled properly. If you have a ... 1. General question: consider asking the question on Stack Overflow with the python-imaging-library tag: * https://stackoverflow.com/questions/tagged/python-imaging-library Do not ask a question in both places. If you think you have found a bug or have an unexplained exception then file a bug report here. 2. Bug report: include a self-contained, copy-pastable example that generates the issue if possible. Be concise with code posted. Guidelines on how to provide a good bug report: * https://stackoverflow.com/help/mcve Bug reports which follow these guidelines are easier to diagnose, and are often handled much more quickly. 3. Feature request: do a quick search of existing issues to make sure this has not been asked before. We know asking good questions takes effort, and we appreciate your time. Thank you. --> ### What did you do? I ran the pillow 12.2.0 test suite on a machine where XCB (X protocol) support is available, but without a running X session. ### What did you expect to happen? All tests should pass. ### What actually happened? `test_grab_x11` failed with: ``` .... > size, data = Image.core.grabscreen_x11(display_name) ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ E OSError: X connection failed: error 5 .... > raise subprocess.CalledProcessError(retcode, args) E subprocess.CalledProcessError: Command '['gnome-screenshot', '-f', '/tmp/tmpqqqjkvf6.png']' returned non-zero exit status 1. ../build/prototype/i386/usr/lib/python3.13/vendor-packages/PIL/ImageGrab.py:135: CalledProcessError -------------------------------------------------------------------------------------- Captured stderr call --------------------------------------------------------------------------------------- (gnome-screenshot:8318): Gtk-WARNING **: 16:20:16.856: cannot open display .... ``` ### What are your OS, Python and Pillow versions? * OS: Oracle Solaris * Python: 3.11 and 3.13 * Pillow: 12.2.0 ```text -------------------------------------------------------------------- Pillow 12.2.0 Python 3.13.12 (main, Mar 24 2026, 07:17:40) [GCC 15.2.0] -------------------------------------------------------------------- Python executable is /bin/python3 System Python files loaded from /usr -------------------------------------------------------------------- Python Pillow modules loaded from /builds/pillow/build/prototype/i386/usr/lib/python3.13/vendor-packages/PIL Binary Pillow modules loaded from /builds/pillow/build/prototype/i386/usr/lib/python3.13/vendor-packages/PIL -------------------------------------------------------------------- --- PIL CORE support ok, compiled for 12.2.0 *** TKINTER support not installed --- FREETYPE2 support ok, loaded 2.14.2 --- LITTLECMS2 support ok, loaded 2.17 --- WEBP support ok, loaded 1.6.0 *** AVIF support not installed --- JPEG support ok, compiled for 9.0 --- OPENJPEG (JPEG2000) support ok, loaded 2.5.3 --- ZLIB (PNG/ZIP) support ok, loaded 1.3.2 --- LIBTIFF support ok, loaded 4.7.1 *** RAQM (Bidirectional Text) support not installed *** LIBIMAGEQUANT (Quantization method) support not installed --- XCB (X protocol) support ok -------------------------------------------------------------------- ```