def add_file(self, file):
            """
            Add the lines of a file to self.list
            """
            if file.is_file():
                with salt.utils.files.fopen(file) as source:
                    for line in source:
                        self.list.append(SourceEntry(line, file=str(file)))
            else:
                log.debug("The apt sources file %s does not exist", file)