subprocess.check_output() is nice, but doesn't help if you want to process the piped data line-by-line.

Currently, that means you have to do the full Popen dance if you want access to each line of output as it becomes available.

This RFE is for a subprocess.iter_output() module level helper that:
1. Starts the subprocess
2. Yield the individual lines of output as they are produced by the subprocess
3. Cleans up (including checking for errors) at the end

This biggest challenge I have noticed so far in exploring this is how to handle timeouts on Windows - on Unix, select.select() can do the job, but that won't handle pipes in the Windows case.