By defaults, `requests` has no timeout on requests, which can lead to
waiting indefinitely. Add a half-second timeout on these; this is
applied _inside_ each retry, not overall -- that is, with retries any
of these functions may take a total of 1.5s.
Use the `no_proxy` proxy, which explicitly disables proxy usage for
particular hosts. This is a slightly cleaner solution than ignoring
all of the environment, as removing proxies is specifically what we
are attempting to accomplish.
The change in #2764 provided a better error message on one of the
three calls into Tornado, but left the other two with the old error
message. `raise_for_status` was used on two out of three.
Use a custom HTTPAdapter to apply this pattern to all requests from
Django to Tornado.
