A step towards a Content-Security-Policy without inline scripts. The
scripts every page or many pages share now load from static files: the
error focus of base.html, the please-wait dialog, the sign-in forms'
password toggle and busy button, the jobs pages' reload while a job
runs, and the start of the job panel and of the VM list's state poll,
whose values come as json_script data. Cancel links go back through a
data-history-back attribute instead of a javascript: URL. The IE8
html5shiv/respond.js block, X-UA-Compatible and shrink-to-fit are gone:
no supported browser reads them.
The 403, 404 and 500 pages said "Oops!" and one generic sentence; a bad
request and a failed CSRF check fell back to Django's plain pages.
Every error page now shares templates/error.html: a card with the status
in a coloured badge with an icon, a heading in plain words, what happened
and what to do, and Back and Home buttons. It uses only theme-defined
Bootstrap classes, so it reads in the light and dark themes alike.
- 400: the request was not accepted; a new address belongs in ALLOWED_HOSTS.
- 403: the account lacks the permission; ask an administrator.
- 403 CSRF: the form's security check failed; reload and submit again,
and where to look when it happens on every form.
- 404: the path, and that the object may be gone or hidden from the account.
- 500: a libvirt failure on a page says the host's data could not be
loaded, under libvirt's message; any other failure says it was logged
and shows the time to give an administrator.
