Faster Google App Engine Managed VM deploys (Python compat env)?
Well, in general, 10 minute deployment isn't that bad. I use AWS Elastic Beanstalk and it's about the same for a full deployment of a production environment. However, this is totally unacceptable for your everyday development.  
Since you use docker, I really don't understand, why not to spin up the same container on your local machine and test it locally before releasing to staging?   
If that is not an option, for some reason, my second bet would be updating code directly inside the container. I've used that trick a lot. As Python a dynamic language, all you need just a fresh copy of your repo, so, you can ssh into your container and check out the code. That said, the feedback loop will be reduced to the time of committing and checking out the code. Additionally, if you set up some hooks on commit, you don't even need to check out the code manually.  
All in all, this is just my two cents and it would be nice to hear more opinions on that really important issue.
We're using Google App Engine (GAE) with Managed VMs for a Python compat environment, and deployments take too much time. I haven't done strict calculations, but I'm sure each deployment takes over 10 mins.
What can we do to accelerate this? Is this more a GAE or a Docker issue? Haven't tried deploying Docker in other platforms so I'm not sure standard/acceptable deployment times.
Having to wait so much to test an app in the staging servers damages our productivity quite a bit. Any help is appreciated. :)