Add a comment to explain the purpose of the explicit_paths list
is_local now takes into account changes done in the configuration file with the sys.path directive. These changes are now stored in locations.explicit_paths
Tests the option of updating the sys.path in the config file
Define the imports at the head of file
Force the instantiation of a new WorkingSet, instead of using the existing one to allow changes to sys.path to take effect in the distributions look up