Write the coverage results.
:param show_missing: Show lines that had no hits.
:param summary: Include coverage summary per module.
:param coverdir: If None, the results of each module are placed in its
directory, otherwise it is included in the directory
specified.
:param ignore_missing_files: If True, counts for files that no longer
exist are silently ignored. Otherwise, a missing file
will raise a FileNotFoundError.