Compositor: Explicitly set device in test scripts

This patch explicitly sets the compositing device in the compositor test
scripts. This is done to make the tests more robust, since a developer
might accordantly save a file with a different device.

tests/python/compositor_cpu_render_tests.py

@@ -15,6 +15,9 @@ try:
 except ImportError:
     inside_blender = False
 
+SET_COMPOSITOR_DEVICE_SCRIPT = "import bpy; " \
+    "bpy.data.scenes[0].render.compositor_device = 'CPU'"
+
 
 def get_arguments(filepath, output_filepath):
     return [
@@ -24,8 +27,8 @@ def get_arguments(filepath, output_filepath):
         "--debug-memory",
         "--debug-exit-on-error",
         filepath,
-        "-P",
-        os.path.realpath(__file__),
+        "-P", os.path.realpath(__file__),
+        "--python-expr", SET_COMPOSITOR_DEVICE_SCRIPT,
         "-o", output_filepath,
         "-F", "PNG",
         "-f", "1"]

tests/python/compositor_realtime_render_tests.py

@@ -15,7 +15,7 @@ try:
 except ImportError:
     inside_blender = False
 
-ENABLE_REALTIME_COMPOSITOR_SCRIPT = "import bpy; " \
+SET_COMPOSITOR_DEVICE_SCRIPT = "import bpy; " \
     "bpy.data.scenes[0].render.compositor_device = 'GPU'"
 
 
@@ -28,7 +28,7 @@ def get_arguments(filepath, output_filepath):
         "--debug-exit-on-error",
         filepath,
         "-P", os.path.realpath(__file__),
-        "--python-expr", ENABLE_REALTIME_COMPOSITOR_SCRIPT,
+        "--python-expr", SET_COMPOSITOR_DEVICE_SCRIPT,
         "-o", output_filepath,
         "-F", "PNG",
         "-f", "1"