See merge request !1714

Fixes handling failed backups and default_exception_handler.

See merge request nexedi/slapos!1685

Stop using deprecated ssl.wrap_socket, and let unset key-file mean
the key is included in cert-file, as is done in python ssl module.
Also let the server crash if specified cert-file or key-file does
not exist, instead of silently falling back to non-TLS http.

Add 'socketpath' and 'abstract' options for path based unix sockets
and abstract unix sockets respectively.

See merge request !1716

See neoppod@f4a5fe3b.

This was sometimes causing false positives, for example if site have
only one hit and this hit takes more than one second, apdex is 0% and
promise failed, it seems useful to at least have a way to disable.

We are discussed on nexedi/slapos!1716 (comment 225941)
an idea of introducing a "minimal number of hits" parameter to not
detect this false positive on sites that are not accessed enough to
calculate a meaningful apdex.

Needed for password authentication to websocket
A bug was discovered in previous version