title: CGI python doesn't print when call getvalue
body: <p>I send a json with ajax jquery and I want to print the data in a txt file with python:
  client:</p>
  
  <pre><code>&lt;html&gt;
  &lt;head&gt;
      &lt;meta http-equiv="content-type" content="text/html; charset=utf-8"&gt;
      &lt;title&gt;test&lt;/title&gt;
      &lt;script src="http://ajax.googleapis.com/ajax/libs/jquery/1.7.2/jquery.min.js"&gt;&lt;/script&gt;
      &lt;script&gt;
          $(function(){
              $('#clickme').click(function(){
                  alert('Im going to start processing');
                  $.ajax({
                      url: "test.py",
                      type: "post",
                      datatype:"json",
                      data: {'key':'value','key2':'value2'},
                      success: function(response){
                          alert(response.message);
                          alert(response.keys);
                      }
                  });
              });
          });
      &lt;/script&gt;
  &lt;/head&gt;
  &lt;body&gt;
      &lt;button id="clickme"&gt; click me &lt;/button&gt;
  &lt;/body&gt;
  </code></pre>
  
  <p></p>
  
  <p>Server:</p>
  
  <pre><code>import json`import cgi`
  fs = cgi.FieldStorage()
  out_file = open("test.txt","w")
  for k in fs.keys(): 
      out_file.write(fs.getvalue(k))
  </code></pre>
  
  <p>but the code doesn't print anything</p>