Tests fail because new Pillow version does not save exif metadata (by default) whereas test case images have it

[bluecarrot16]

Pillow 9.4.0 https://github.com/python-pillow/Pillow/releases/tag/9.4.0 no longer saves EXIF metadata to PNG images by default python-pillow/Pillow#6804 . This breaks many current tests which rely on comparing output with images generated with earlier versions of Pillow and thus containing EXIF metadata.

Two things,

1. We should pin the version of Pillow used
2. We should either update the save functions to explicitly add exif or update the tests to compare file contents, ignoring metadata.