Port `event_rpcgen.py` and `test/check-dumpevents.py` to Python 3.
These scripts remain compatible with Python 2.
(cherry picked from commit 8b0aa7b36a3250fad4953f194c8a94ab25032583)
Use python2 rather than python
python may refer to either python2 or python3 so rather by explicit by
using python2.
See PEP 394 - http://www.python.org/dev/peps/pep-0394/ for more
details.
Add a unit test for event_base_dump_events()
This function uses a C program to generate its output, and then uses a
Python program to check it for correctness. On systems without
Python, we just make sure that the C program doesn't crash.
It's likely that we should be requiring some particular python version.
This is an alpha, though: I'm sure somebody will tell us which.
