Extension of PR #3186 for the caplog feature.

When a test fails and we are about the enter the debugger, we first print the traceback and the captured stdout and stderr. We need to add the captured logs. This is being opened as a separate ticket because caplog was added in the features branch, so if this issue is fixed before it gets merged, target the features branch for this issue as well.

See discussion here: https://github.com/pytest-dev/pytest/pull/3186/files#r166777807