Catch other pymodbus import exceptions on Python3
Clean up logging and fix Python2/3 compatibility, EINTR handling
o Remove logging.basicConfig except in main path, and ensure that no
  imported modules invoke logging calls, to avoid logging complaining
  that there is no Null logger.
o Ensure that logging level extensions report calling function name
o Make web.py and pymodbus requirements-optional.txt, and only install
  them by default in Python2.
o Make cpppo.enip.server.main and cpppo.enip.server.client.main
  use argparse correctly, to get argv[1:] by default.
o Correctly implement log file rotation.
o Correctly test for EtherNet/IP CIP registers response.
o Correct handling of EINTR in cpppo.network.readable decorator
o Ship enip_server and enip_client as console_scripts in setup.py
o Version 1.9.6