Log Message:
py-zopfli: updated to 0.2.1

v0.2.1
[zopfli.png] Only print debug info to console output when -v/--verbose flag is used.

v0.2.0
Dropped support for EOL Python 2.7 and 3.6, require Python 3.7+.
Added support for compressing PNGs via zopfli.png.optimize method. Also \ 
available from the command line as python -m zopfli.png; mimics the upstream's \ 
zopflipng c++ executable.