Refactor some TransportPCE code

Experience shows that along each sprint, a given number of refactoring changes is proposed. Some of them are intended to resolve specific issues like as an example pylint issues, others are simply devoted to improving the readability of the code.
This can apply to both TransportPCE 'business' code and test code (Junit tests or even python functional tests).
This JIRA ticket allows us to track all refactoring actions that are not necessarily linked to another development card.