COMPATIBILITY

# This code exists in branches for supporting different python versions.
# The project aims to have as few python version support branches as possible,
# so python version branches are created where otherwise would be impossible
# or would lead to unreasonably complicated or messy code.
# The project aims to have the python version branches as similar as possible,
# which has some consequences:
#  - not using new APIs, e.g. using poll and not the superior epoll
#  - should explain some backward code
#
# Initialy this code aimed to work with python version starting with 2.4.
# Supporting 2.4 and 3.5 seemed impossible, or unreasonably complicated.
# One reason is incompatible exception handling syntax.