Returns the section heading for the issue, or None if this issue should be ignored.

def issue_section(issue):
    """Returns the section heading for the issue, or None if this issue should be ignored."""
    labels = issue.get('labels', [])
    for label in labels:
        if not label['name'].startswith('type: '):
            continue

        if label['name'] in LOG_SECTION:
            return LOG_SECTION[label['name']]
        elif label['name'] in IGNORE_ISSUE_TYPE:
            return None
        else:
            logging.warning('unknown issue type: "{}" for: {}'.format(label['name'], issue_line(issue)))

    return None