Comment 4 for bug 788309

def search(template_file, mlist=None, language=None):
    """Generator that provides file system search order.

    This is Mailman's internal template search algorithm. The first locations
    searched are within the $var_dir/templates directory, allowing a site to
    override a template for a specific mailing list, all the mailing lists in
    a domain, or site-wide.

    The <language> path component is variable, and described below.

    * The list-specific language directory
      <var_dir>/templates/lists/<mlist.fqdn_listname>/<language>

    * The domain-specific language directory
      <var_dir>/templates/domains/<mlist.mail_host>/<language>

    * The site-wide language directory
      <var_dir>/templates/site/<language>

    The <language> path component is calculated as follows, in this order:

    * The `language` parameter if given
    * `mlist.preferred_language` if given
    * The server's default language
    * English ('en')

    Languages are iterated after each of the four locations are searched. So
    for example, when searching for the 'foo.txt' template, where the server's
    default language is 'fr', the mailing list's (<email address hidden>) language
    is 'de' and the `language` parameter is 'it', these locations are searched
    in order:

    * <var_dir>/<email address hidden>/it/foo.txt
    * <var_dir>/templates/domains/example.com/it/foo.txt
    * <var_dir>/templates/site/it/foo.txt

    * <var_dir>/<email address hidden>/de/foo.txt
    * <var_dir>/templates/domains/example.com/de/foo.txt
    * <var_dir>/templates/site/de/foo.txt

    * <var_dir>/<email address hidden>/fr/foo.txt
    * <var_dir>/templates/domains/example.com/fr/foo.txt
    * <var_dir>/templates/site/fr/foo.txt

    * <var_dir>/<email address hidden>/en/foo.txt
    * <var_dir>/templates/domains/example.com/en/foo.txt
    * <var_dir>/templates/site/en/foo.txt

    After all those paths are searched, the final fallback is the English
    template within the Mailman source tree.

    * <source_dir>/templates/en/foo.txt
    """