Two new functions were introduced:


get_evolutions_module_name() returns the name of the .evolutions

  module for a given app. This encompasses the logic that was in

get_evolutions_module(), handling built-in evolutions and custom

  evolutions along with app-provided evolutions.


get_evolution_module() returns the module for a specific evolution

  in an app.


get_app_mutations() has been updated to use the new

get_evolution_module(). Some upcoming functions will make further use

of both functions.
Unit tests were added for these new functions.

Unit tests pass.