title: Fabric asks for password even though I can SSH using credential
body: <p>I'm having an odd problem while deploying a Django site using Fabric. I've configured two servers to use key files for login. I can SSH into both without a password. I can run fab on one correctly,</p>
  
  <pre><code>$ fab live pull
  [mysite.com] Executing task 'pull'
  [mysite.com] run: test -d proj
  [mysite.com] run: test -d proj/.git
  [mysite.com] run: git pull origin master
  ...
  </code></pre>
  
  <p>while the other server asks for a password: </p>
  
  <pre><code>$ fab staging pull
  [dev.mysite.com] Executing task 'pull'
  [dev.mysite.com] run: test -d proj
  [dev.mysite.com] Login password: 
  </code></pre>
  
  <p>The fabfile is set up pretty explicitly</p>
  
  <pre><code>def staging():
      env.hosts = ['dev.mysite.com']
      env.user = 'bamboo'
      env.key_filename = '~/.ssh/id_dsa_bamboo'
  </code></pre>
  
  <p>And running ssh directly from the command line works</p>
  
  <pre><code>$ ssh bamboo@dev.mysite.com -i ~/.ssh/id_dsa_bamboo
  Last login: Wed Apr 11 06:24:28 2012 from xxx.xxx.xx.xx
  [bamboo@dev ~]$ 
  </code></pre>
  
  <p>I also tried setting <code>env.use_ssh_config = True</code> and running with <code>~/.ssh/config</code> set to</p>
  
  <pre><code>Host dev.mysite.com                                                                           
      User bamboo                                                                              
      IdentityFile ~/.ssh/id_dsa_bamboo                                                        
      ForwardAgent yes
  </code></pre>
  
  <p>Any ideas what could be going on? Thanks for the help. </p>