Google says: "if the task you're deferring* relies on modules* that aren't on the import path by default, you need to give it a helping hand."
"path modifications": in your link: "you should not change sys.path when you have more than one thread running." The Google example: sys.path.*append*(os.path.join(os.path.dirname(__file__), 'lib')) Is not changing sys.path, but appending to it.