If you set ANSIBLE_KEEP_REMOTE_FILES=1 (environment variable only) in the latest git, the files will be left around. This may help with debugging module failures, as you can use this with -vvv to see what commands are run, and then rerun them as needed, and can even retry with different arguments as well.
This should be a helpful debugging tool when troubleshooting those rare but slightly annoying module failures, without having to resort to ./hacking/test-module
--Michael