Build pubnote string from parts (reverse of split_pubnote).

def build_pubnote(title, volume, page_start=None, page_end=None, artid=None):
    """Build pubnote string from parts (reverse of split_pubnote)."""
    if title and volume and artid and artid != page_start:
        pubnote_format = u'{title},{volume},{artid}'
    elif title and volume and page_start and page_end:
        pubnote_format = u'{title},{volume},{page_start}-{page_end}'
    elif title and volume and page_start:
        pubnote_format = u'{title},{volume},{page_start}'
    elif title and volume:
        pubnote_format = u'{title},{volume}'
    else:
        return None

    return pubnote_format.format(
        title=title, volume=volume, page_start=page_start, page_end=page_end, artid=artid
    )