From looking at "what" Git Bash, it would seem to be a cut down version of cygwin. I have just run "python3 -m http.server 8000", and get the following log output:
$ python3 -m http.server 8000
Serving HTTP on 0.0.0.0 port 8000 (http://0.0.0.0:8000/) ...
127.0.0.1 - - [04/Jun/2017 20:15:10] "GET / HTTP/1.1" 200 -
127.0.0.1 - - [04/Jun/2017 20:15:10] code 404, message File not found
127.0.0.1 - - [04/Jun/2017 20:15:10] "GET /favicon.ico HTTP/1.1" 404 -
127.0.0.1 - - [04/Jun/2017 20:15:10] code 404, message File not found
127.0.0.1 - - [04/Jun/2017 20:15:10] "GET /favicon.ico HTTP/1.1" 404 -
It would seem that git bash is not logging (outputting) correctly.
Trying running "python3 -m http.server 8000" in virtualbox / vagrant -> with Ubuntu or Centos.