title: Python make datetime offset aware
body: <p>I want to get the offset for datetime and make an aware string.  <br/></p>
  
  <p>The following IDLE code works:  <br/></p>
  
  <p><code>Python 3.6.5 (default, Apr  1 2018, 05:46:30)</code><br>
  <code>[GCC 7.3.0] on linux</code></p>
  
  <pre><code>import datetime
  date_now = datetime.datetime.now()
  date_now_with_offset = date_now.astimezone()
  print(date_now_with_offset)
  2018-06-03 17:48:50.258504-05:00
  </code></pre>
  
  <p>The following code in a script gives an error: <br/></p>
  
  <pre><code>import datetime
  date_now = datetime.datetime.now()
  date_now_with_offset = date_now.astimezone()
  print(date_now_with_offset)
  
  TypeError: Required argument 'tz' (pos 1) not found
  </code></pre>
  
  <p>I realize that offset and timezone are different but at any given moment
  the local time should be offset the same as an accurate timezone offset even though timezone offset may fluctuate during the year.  <br/></p>
  
  <p>What is happening and why?  What is the best solution?  <br/></p>