Add HTTP debugging output

While debugging client/server issues, I needed to inspect the actual HTTP requests sent by the client.

I ended up adding something like https://stackoverflow.com/questions/16337511/log-all-requests-from-the-python-requests-module#57325050 (last answer snippet sending output to stdout) in debusine_http_client.py, which sets the logging level and output of urllib3.

I believe this would be worth adding permanently.