Comment 7 for bug 1805332

Reviewed: https://review.openstack.org/644839
Committed: https://git.openstack.org/cgit/openstack/glance_store/commit/?id=9c8364bacfbe831a755b096a92fb7da2ff3c878d
Submitter: Zuul
Branch: stable/stein

commit 9c8364bacfbe831a755b096a92fb7da2ff3c878d
Author: wangxiyuan <email address hidden>
Date: Tue Nov 27 14:50:50 2018 +0800

    Prevent unicode object error from zero-byte read

    During large file uploads under py3, we are occasionally seeing a
    "unicode objects must be encoded before hashing" error even though
    we are reading from a byte stream. From what I can tell, it looks
    like it's happening when a zero-byte read is requested, so we handle
    that case explicitly. This is a band-aid fix; we still need to track
    down the source.

    Co-authored-by: wangxiyuan <email address hidden>
    Co-authored-by: Brian Rosmaita <email address hidden>

    Related-bug: #1805332
    Change-Id: Ia7653f9fcbe902abc203c10c80ab44a641a4d8f9
    (cherry picked from commit 1d25a2b7a21e95766f9fee378b3d0802d392a85f)