Swift3 should report a clear an unambiguous error on region mismatch for v4 signatures

[Tim Burke]

Currently, we punt to the auth middleware to use a swift3-provided scope (including region), and 403 when the signature doesn't match. This:

 1. isn't helpful for the client -- API users are left needing to contact operators to find out what went wrong, and
 2. doesn't match what AWS does:

S3ResponseError: 400 Bad Request
<?xml version="1.0" encoding="UTF-8"?>
<Error><Code>AuthorizationHeaderMalformed</Code><Message>The authorization header is malformed; the region 'us-east-1' is wrong; expecting 'us-west-2'</Message><Region>us-west-2</Region><RequestId>...</RequestId><HostId>...</HostId></Error>

All this despite the fact that we've got the entire credential scope in hand -- https://github.com/openstack/swift3/blob/v1.11/swift3/request.py#L206-L207

[OpenStack Infra (hudson-openstack)]

Change abandoned by Tim Burke (<email address hidden>) on branch: master
Review: https://review.openstack.org/448764
Reason: Submitted against s3api as https://review.openstack.org/#/c/575836/

[Tim Burke (1-tim-z)]

Re-targetted to swift, now that s3api lives there.

[OpenStack Infra (hudson-openstack)]

Reviewed: https://review.openstack.org/575836
Committed: https://git.openstack.org/cgit/openstack/swift/commit/?id=27d852395fb01edd7955fdea18616a16c919a214
Submitter: Zuul
Branch: master

commit 27d852395fb01edd7955fdea18616a16c919a214
Author: Tim Burke <email address hidden>
Date: Fri Jun 15 13:15:34 2018 -0700

    Give better errors for malformed credentials

    This lets clients know when they used the wrong region,
    for example.

    Change-Id: Id3ac41e994705d3befe32df60ff4241c334a78b7
    Closes-Bug: #1674842

[OpenStack Infra (hudson-openstack)]

This issue was fixed in the openstack/swift 2.20.0 release.