If a user sends a Range header with no satisfiable ranges, we send back
a 416 Requested Range Not Satisfiable response. Previously however,
there would be no indication of the size of the object they were
requesting, so they wouldn't know how to craft a satisfiable range. We
*do* send a Content-Length, but it is (correctly) the length of the
error message.
The RFC [1] has an answer for this:
> A server generating a 416 (Range Not Satisfiable) response to a
> byte-range request SHOULD send a Content-Range header field with an
> unsatisfied-range value, as in the following example:
>
> Content-Range: bytes */1234
>
> The complete-length in a 416 response indicates the current length of
> the selected representation.
Now, we'll send a Content-Range header for all 416 responses, including
those coming from the object server as well as those generated on a
proxy because of the Range mangling required to support EC policies.
[1] RFC 7233, section 4.2, although similar language was used in RFC
2616, sections 10.4.17 and 14.16
Change-Id: I80c7390fc6f84a10a212b0641bb07a64dfccbd45
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