Fixed #21618 -- Added hints about openlayers.js hosting

    This is the default widget used by all GeoDjango form fields.

    ``template_name`` is ``gis/openlayers.html``.

    ``OpenLayersWidget`` and :class:`OSMWidget` use the ``openlayers.js`` file

    hosted on the ``openlayers.org`` Web site. This works for basic usage

    during development, but isn't appropropriate for a production deployment as

    ``openlayers.org/api/`` has no guaranteed uptime and runs on a slow server.

    You are therefore advised to subclass these widgets in order to specify

    your own version of the ``openlayers.js`` file in the ``js`` property of

    the inner ``Media`` class (see :ref:`assets-as-a-static-definition`). You

    can host a copy of ``openlayers.js``

    `tailored to your needs`_ on your own server or refer to a copy from a

    content-delivery network like http://cdnjs.com/. This will also allow

    you to serve the JavaScript file(s) using the ``https`` protocol if needed.

    .. _tailored to your needs: http://docs.openlayers.org/library/deploying.html

``OSMWidget``

.. class:: OSMWidget

    This widget uses an OpenStreetMap base layer (Mapnik) to display geographic

    objects on.

    ``template_name`` is ``gis/openlayers-osm.html``.

    The :class:`OpenLayersWidget` note about JavaScript file hosting above also

    applies here. See also this `FAQ answer`_ about ``https`` access to map

    tiles.

    .. _FAQ answer: https://help.openstreetmap.org/questions/10920/how-to-embed-a-map-in-my-https-site