Pillow 8 support

[jensens]

see https://github.com/plone/buildout.coredev/pull/687

[mister-roboto]

@jensens thanks for creating this Pull Request and help improve Plone!

To ensure that these changes do not break other parts of Plone, the Plone test suite matrix needs to pass.

Whenever you feel that the pull request is ready to be tested, either start all jenkins jobs pull requests by yourself, or simply add a comment in this pull request stating:

@jenkins-plone-org please run jobs

With this simple comment all the jobs will be started automatically.

Happy hacking!

[jensens]

@jenkins-plone-org please run jobs

[jensens]

The Plone 5.2/Py 2.7 failing test is unrelated.

We should branch away for Py3/Plone 6 only here.

[mauritsvanrees]

Ah, the 2.7 PR job failed with an unrelated error, but also an actual error in PlonePAS, but this was somehow not reported in the summary. So after merge, the 5.2-2.7 job fails:

File "/home/jenkins/workspace/plone-5.2-python-2.7/src/Products.PlonePAS/src/Products/PlonePAS/utils.py", line 65, in Products.PlonePAS.utils.scale_image
Failed example:
    sneaky = BytesIO('��<div>Evil!!!</div>'.encode("utf-8"))
Exception raised:
    Traceback (most recent call last):
      File "/srv/python2.7/lib/python2.7/doctest.py", line 1315, in __run
        compileflags, 1) in test.globs
      File "<doctest Products.PlonePAS.utils.scale_image[12]>", line 1, in <module>
        sneaky = BytesIO('��<div>Evil!!!</div>'.encode("utf-8"))
    UnicodeDecodeError: 'ascii' codec can't decode byte 0xff in position 0: ordinal not in range(128)

I see why you wanted to branch away for Py3/Plone 6 only here. Putting effort into UnicodeDecodeErrors for 2.7 is not what I want. I will create a branch 6.x and use that in coredev 5.2.

[mauritsvanrees]

All done.