[Checkins] [zopefoundation/Zope] aafe58: Improve solidity of the ``debugError`` method (#831)

[Alessandro Pisa]

  Branch: refs/heads/4.x
  Home:   https://github.com/zopefoundation/Zope
  Commit: aafe5857e5114427cd6df9ebbe5c7c2d813aa364
      https://github.com/zopefoundation/Zope/commit/aafe5857e5114427cd6df9ebbe5c7c2d813aa364
  Author: Alessandro Pisa <alessandro.pisa at gmail.com>
  Date:   2020-05-16 (Sat, 16 May 2020)

  Changed paths:
    M CHANGES.rst
    M src/ZPublisher/HTTPResponse.py
    M src/ZPublisher/tests/testHTTPResponse.py

  Log Message:
  -----------
  Improve solidity of the ``debugError`` method (#831)

Backport of #830 to the 4.x branch