The logs for ci.jenkins.io are filled with:

WARNING: A connection to https://api.github.com/ was leaked. Did you forget to close a response body?

Over 1500 instances since upgrading to SCM API 2.x plugins last Friday (2017-03-03).

% docker logs jenkins 2>&1 | grep leak -c
1558
%

I'm not sure if this is a superfluous warning, or something more concerning.