def fallbackPackage(package_name, fallback_package_name):
importer = Finder(package_name, fallback_package_name)<EOL>sys.meta_path.append(importer)<EOL>
if an import cannot be resolved
import from fallback package

example:
from [package_name].doesnt_exist import Foo

results in 
from [fallback_package_name].doesnt_exist import Foo