List attachment for the specified fullname.

def list_attachments(fullname):
    """ List attachment for the specified fullname.
    """
    parent, filename = os.path.split(fullname)
    filename_without_ext, ext = os.path.splitext(filename)
    attachments = []
    for found_filename in os.listdir(parent):
        found_filename_without_ext, _ = os.path.splitext(found_filename)
        if filename_without_ext == found_filename_without_ext and found_filename != filename:
            attachments.append(os.path.join(parent, found_filename))
    return attachments