SceneTestCase : Improve error message for `assertPathExists()`.
SceneTestCase : Improve error message for `assertPathExists()`.

lucienfostier/gaffer,andrewkaufman/gaffer,andrewkaufman/gaffer,lucienfostier/gaffer,johnhaddon/gaffer,chippey/gaffer,johnhaddon/gaffer,boberfly/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,lucienfostier/gaffer,hradec/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,ImageEngine/gaffer,boberfly/gaffer,GafferHQ/gaffer,hradec/gaffer,johnhaddon/gaffer,chippey/gaffer,chippey/gaffer,hradec/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,GafferHQ/gaffer,chippey/gaffer,hradec/gaffer,ImageEngine/gaffer,ImageEngine/gaffer,andrewkaufman/gaffer,GafferHQ/gaffer,appleseedhq/gaffer,ivanimanishi/gaffer,boberfly/gaffer,ivanimanishi/gaffer,ImageEngine/gaffer,hradec/gaffer,lucienfostier/gaffer,ivanimanishi/gaffer,johnhaddon/gaffer,appleseedhq/gaffer,boberfly/gaffer,ivanimanishi/gaffer,appleseedhq/gaffer