Comment 2 for bug 2040178

Reviewed: https://review.opendev.org/c/openstack/swift/+/893578
Committed: https://opendev.org/openstack/swift/commit/4a37a2976bb0f1ff5c6fd20800887e1e848c9bea
Submitter: "Zuul (22348)"
Branch: master

commit 4a37a2976bb0f1ff5c6fd20800887e1e848c9bea
Author: Clay Gerrard <email address hidden>
Date: Wed Oct 11 09:33:46 2023 -0500

    slo: refactor GET/HEAD response handling

    This patch reorganizes the SLO read response handling. The main goal
    was to push the response header replacement for both GET/HEAD SLO and
    multipart-manifest=get paths all into a common return path. A new
    RespAttrs primitive is used to carry around some metadata details from
    requests made in SLO. The authors hope these changes make the code more
    easily readable and easier to modify.

    Drive-By: add new "friendly_close" function in common.utils so we can
    drain empty/error responses more confidently (and use it in swob and
    request_helpers).

    Drive-By: the tests added in the Related-Change discovered a 500 on
    If-[Un]Modified-Since conditional GET requests - it probably wasn't
    important, but this refactor fixed it on accident as a side effect.

    Closes-Bug: #2040178
    Co-Authored-By: Alistair Coles <email address hidden>
    Co-Authored-By: Ashwin Nair <email address hidden>
    Related-Change-Id: I54094f3d2098f56b755ec19cc9315d06a6ca8b15
    Change-Id: Idc84e70539fc7480b6ecb86e2f0da904baf2c727