DerivationFrameworkCore: Python 3 fixes

Reapply python 3 fixes clobbered by last change.

This merge request affects 1 package:

• PhysicsAnalysis/DerivationFramework/DerivationFrameworkCore

added Derivation master review-pending-level-1 labels

CI Result FAILURE (hash 54b7d869)

	Athena	AthSimulation	AnalysisBase	AthGeneration
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
AnalysisBase: number of compilation errors 0, warnings 0
AthGeneration: number of compilation errors 0, warnings 0
For experts only: Jenkins output [CI-MERGE-REQUEST-CC7 13894]

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

merged

mentioned in commit 1c58befd

added sweep:ignore label