some flake8
Add a test for PalmImagePlugin.py
Ensure rowbytes is an integer (fix for Python 3)
Refactor and add two more tests
Merge branch 'master' into HEAD
Failing test for messed up P image on write only format
Skip known bad tests
Merge from master
Merge pull request #776 from wiredfool/palm

Palm image test
Update CHANGES.rst [CI skip]