title: How to find the timezone name from a tzfile in python
body: <p>Is it possible to get the inverse of this operation:</p>
  
  <pre><code>import dateutil.tz
  tz_ny = dateutil.tz.tz.gettz('America/New_York')
  print(type(tz_ny))
  print(tz_ny)
  </code></pre>
  
  <p>This prints:</p>
  
  <pre><code>dateutil.tz.tz.tzfile
  tzfile('/usr/share/zoneinfo/America/New_York')
  </code></pre>
  
  <p>How to recover 'America/New_York' given tz_ny of type tzfile?</p>
  
  <p>N.B. <code>tz_ny.tzname(datetime.datetime(2017,1,1))</code> return 'EST' or 'EDT' if the date is in the summer.</p>