title: docker java7 install fail
body: <p>I'm trying to install java7 via ppa (RUN  add-apt-repository ppa:webupd8team/java -y) in my docker image but it fails with this error:</p>
  
  <pre><code>returned a non-zero code: 127
  </code></pre>
  
  <p>The following are suggested ways to install correctly but it's not working. I've tried both ppas as well. </p>
  
  <pre><code>RUN  apt-get install python-software-properties -y
  RUN  add-apt-repository ppa:webupd8team/java -y
  #RUN add-apt-repository ppa:eugenesan/java -y
  RUN apt-get update
  RUN  apt-get install oracle-java7-installer -y
  </code></pre>
  
  <p>Here is the log output:</p>
  
  <pre><code>Step 28 : RUN  add-apt-repository ppa:webupd8team/java -y
   ---&gt; Running in b278761a4209
   [91m/bin/sh: 1: add-apt-repository: not found
   [0m 
  </code></pre>
  
  <p>So...I need to find out where/if this command exist in a helper lib or what:</p>
  
  <pre><code>add-apt-repository
  </code></pre>
  
  <p>add-apt-repository appears to be a part of the python-software-properties install. I don't see any real errors in that step except for these messages which pop up in other areas of the build. So I <em>assume</em> that if I can resolve this issue the aforementioned python step will install as needed:</p>
  
  <pre><code>    [91mdebconf: unable to initialize frontend: Dialog
       debconf: (TERM is not set, so the dialog frontend is not usable.)
       debconf: falling back to frontend: Readline
       [0m[91mdebconf: unable to initialize frontend: Readline
       debconf: (This frontend requires a controlling tty.)
       debconf: falling back to frontend: Teletype
       [0m[91mdpkg-preconfigure: unable to re-open stdin: 
  </code></pre>
  
  <p>So. How to set a term or dialog up? I thought the -y allowed this</p>