I did a search and find the issue 1947, however it's set to "not a bug". In its last note, it's suggested a 'packaging/environment issue'. But since I can reliably reproduce the issue with the "official python package"(that installed by the system, such as I am not building the python from source), Also, the same issue does not occurred on python 2.6.2, but 3.4.3 and 3.5.1. Even though it seems the "AssertionError" message is non-harmful but it's still a bit annoying. I am wondering if you can take a look my issue?

Please compile the attached source codes to reproduce my issue. Note that it only occurred when we (explicitly or implicitly) import the 'threading' module. If we comment out that line, it works fine.