Create_terrain.py script issues random crc16 warnings

When using the create_terrain.py script, running on Ubuntu 20.04 with python 3.8.2, I randomly get the following two warnings:

1. create_terrain.py:205: DeprecationWarning: PY_SSIZE_T_CLEAN will be required for '#' formats
block.crc = crc16.crc16xmodem(buf)

2. create_terrain.py:223: DeprecationWarning: PY_SSIZE_T_CLEAN will be required for '#' formats
crc2 = crc16.crc16xmodem(buf[:1821])

Is this expected?
Update: I loaded up a virtual Ubuntu 18.04 with python 3.6.9 and I don't get any of the crc16 errors. So something with python 3.8 and the crc16 module I suspect. A hash of the files show no differences between them so that answers the question that the python 3.8 files should be ok.

Start with create_terrain.py at lines 205 and 223, where crc16.crc16xmodem is called, and compare the behavior under Python 3.8 versus Python 3.6. Investigate the crc16 module compatibility and determine whether the warnings are expected; done means the cause and any required change or documentation are established.

Written by the indexing model from the issue text.