Quicker and more transparent feedback on command progress

[ilazakis]

All commands that end up running shell scripts (e.g. build, push) are using subprocess.check_output for execution which only returns the output after the script executing subprocess exits.

It would be nice to have more immediate feedback of what's happening. Pushing to ECR for example can take a really long time to execute — sometimes hours — but a user only sees the following on the command line.

Started pushing Docker image to AWS ECS. It will take some time. Please, be patient...

It would be nice to have some indication of progress across the API since many (most?) commands have long execution time potential.

Suggestions

Use an alternative method of calling subprocess that allows streaming of output or switch to using Python scripts and a corresponding Python docker client.