fix sleuth error for python3

[IcedLimeTea]

In the environments of ubuntu20.04 and python3.8, the original python source code cannot correctly install the sleuth dependent library. Therefore, the source code of the sleuth dependent library was rewritten to adapt to the ubuntu20.04 and python3.8 environments. Moreover, add pip install . in Makefile.in to easily install sleuth. This is my first time making pull requests, if there is anything inappropriate or needs improvement, please guide me. Thank you.🙂