title: Python ConfigParser Checking existence of both Section and Key Value
body: <p>Using ConfigParser's <code>has_section()</code> method I can check if a section exists in a file, such as:</p>
  
  <pre><code>config.has_section(section_name) 
  </code></pre>
  
  <p>What would be a command to check if a <strong>key</strong> exists as well? 
  So it would be possible to verify that both a section and key exists before querying the value using:</p>
  
  <pre><code>value = config.get(section, key)
  </code></pre>
  
  <p>Thanks in advance!</p>