Plone 5.2 should support both Python2.7 and Python3.X , but Pillow < 8.0.0 cannot find zlib on Macs with the latest OS X and running on the new M1 architecture:

  File "/var/folders/bc/qzs1h_3n2dggkdkm5t07_2m80000gn/T/easy_install-dm3pwbq3/Pillow-6.2.2/setup.py", line 687, in build_extensions
__main__.RequiredDependencyException: zlib

This was fixed in Pillow 8.0.0: (Added homebrew zlib include directory #4842 [radarhere]) But Pillow > 6.2.2 no longer supports Python 2.7

Could we maybe add a specific version override for python3: that pins Pillow to 8.00/8.1.0 for python3 but keeps it to 6.2.2 for python2?