title: docker-compose up hangs forever. How to debug?
body: <p>I have a project with a dockerfile and a docker-compose.yml for deploying it. But if I run <code>docker-compose up</code>, the command prints <code>Building app</code> and hangs forever. I do not see any steps being performed. It isn't downloading images either since there's no network traffic, and the images used are available in the cache.</p>
  
  <p>How can I go about debugging and fixing this issue on my machine? Is there a verbose option for docker(-compose) that I could use?</p>