title: The --backends flag for Google App Engine's dev_appserver doesn't seem to be supported?
body: <p>I'm trying to test out my Google App Engine Python backend code locally.  According to the docs there is a flag, --backends, for dev_appserver that will let you run them locally.  I'm using 1.8, and I get this error when I try to use that flag:</p>
  
  <p>error:</p>
  
  <p>dev_appserver.py: error: unrecognized arguments: --backends</p>
  
  <p>Am I doing something wrong, or does this flag not exist?  The docs say it does.  But it's not listed on the help output for dev_appserver either.  </p>
  
  <p>I also got this error with the previous 1.7.X version (updated today)</p>