Make it possible to put the site in maintenance mode
By specifying the UTC date from which the maintenance shoulds start,
developers can put the site in 'maintenance' mode.
Also redirect to /maintenance if we get a CapabilityDisabledError.
Patch by: Sverre Rabbelier
{% comment %}
Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
You may obtain a copy of the License at
http://www.apache.org/licenses/LICENSE-2.0
Unless required by applicable law or agreed to in writing, software
distributed under the License is distributed on an "AS IS" BASIS,
WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
See the License for the specific language governing permissions and
limitations under the License.
{% endcomment %}
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN">
<html lang="en">
<head>
<title>500 Server Error</title>
</head>
<body><h1>500 Server Error</h1></body>
</html>