skip ImageGrab test on Windows in Docker

Tests/helper.py

@@ -282,6 +282,19 @@ def is_win32():
     return sys.platform.startswith("win32")
 
 
+def is_win32_docker():
+    try:
+        import winreg
+
+        key = winreg.OpenKey(
+            winreg.HKEY_LOCAL_MACHINE, r"SYSTEM\CurrentControlSet\Control"
+        )
+        winreg.QueryValueEx(key, "ContainerType")  # fails if not in Docker container
+        return True
+    except (ImportError, OSError):
+        return False
+
+
 def is_pypy():
     return hasattr(sys, "pypy_translation_info")
 

Tests/test_imagegrab.py

@@ -6,13 +6,19 @@ import pytest
 
 from PIL import Image, ImageGrab
 
-from .helper import assert_image, assert_image_equal_tofile, skip_unless_feature
+from .helper import (
+    assert_image,
+    assert_image_equal_tofile,
+    is_win32_docker,
+    skip_unless_feature,
+)
 
 
 class TestImageGrab:
     @pytest.mark.skipif(
         sys.platform not in ("win32", "darwin"), reason="requires Windows or macOS"
     )
+    @pytest.mark.skipif(is_win32_docker(), reason="running on headless Windows")
     def test_grab(self):
         for im in [
             ImageGrab.grab(),