EventInfo: Python 3 fixes

Update to work with python 3.

Also add flake8 fixes.

This merge request affects 1 package:

• Event/EventInfo

Adding @rbianchi as watcher

added EDM master review-pending-level-1 labels

CI Result SUCCESS (hash 3f8e944d)

	Athena	AthSimulation
externals
cmake
make
required tests
optional tests

Full details available on this CI monitor view
Athena: number of compilation errors 0, warnings 0
AthSimulation: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 10296]

added review-approved label and removed review-pending-level-1 label

merged

mentioned in commit bf1b131d

added sweep:ignore label