src/vs/platform/files/common/fileService.ts/FileService/throwIfFileIsReadonly
class FileService:	private throwIfFileIsReadonly(resource: URI, stat: IStat): void {
		if ((stat.permissions ?? 0) & FilePermission.Readonly) {
			throw new FileOperationError(localize('err.readonly', "Unable to modify readonly file '{0}'", this.resourceForError(resource)), FileOperationResult.FILE_PERMISSION_DENIED);
		}
	}