[Checkins] [zopefoundation/ZODB] d3b2e2: Backport from 4.0 and later

[GitHub]

  Branch: refs/heads/gotcha-opened-file-backport
  Home:   https://github.com/zopefoundation/ZODB
  Commit: d3b2e2ec98f958ad20fe20690fde8ca7cdb42af1
      https://github.com/zopefoundation/ZODB/commit/d3b2e2ec98f958ad20fe20690fde8ca7cdb42af1
  Author: Godefroid Chapelle <gotcha at bubblenet.be>
  Date:   2017-04-19 (Wed, 19 Apr 2017)

  Changed paths:
    M src/ZODB/blob.py

  Log Message:
  -----------
  Backport from 4.0 and later