[Checkins] [zopefoundation/Zope] 66a400: Prevent Error in isHTML()

[Michael Howitz]

  Branch: refs/heads/icemac-patch-1
  Home:   https://github.com/zopefoundation/Zope
  Commit: 66a40099f7e35ab239e1d5b768824798af38aaa2
      https://github.com/zopefoundation/Zope/commit/66a40099f7e35ab239e1d5b768824798af38aaa2
  Author: Michael Howitz <mh at gocept.com>
  Date:   2019-04-30 (Tue, 30 Apr 2019)

  Changed paths:
    M src/ZPublisher/HTTPResponse.py

  Log Message:
  -----------
  Prevent Error in isHTML()

If the parameter cannot be decoded none of the following checkes can lead to `True`.
The last one even breaks on Python 3 because it tries to find a `text` in a `bytes` object.