BUG: update reqirements

Bug

Error description

Some python packages cause errors on installation.

Error message

ModuleNotFoundError: No module named 'appdirs'

First guess on error origin

Some old / outdated packages are somehow not findable for pip anymore.

Error origin

Solution

Either add >= for these packages or just update the version number.

• absl-py==0.9.0 -> absl-py==0.11.0
• locket==0.2.0 -> locket==0.2.1
• py==1.8.1 -> py>=1.8.2
• other packages to update?