Clean up usage of raw strings

[evqna]

The strings 'bandit' and 'gosec' appear in several places in the code, it may be time to clean that up.

[MVrachev]

How do you imagine this cleanup?
You will put a const variable called 'bandit' or 'python_linter' or what?

[evqna]

Preferably using an enumeration or some other type-safe construct that prevents mis-typing or introducing bugs by not keeping the different uses in sync

[evqna]

A gloal const string could also work but it still requires a bunch of code switches in a few places to call the correct code for each linter.