title: Python f-string formatting not working with strftime inline
body: <p>I'm hitting an odd error that I'm trying to understand. Doing some general code cleanup and converting all string formatting to f-strings. This is on Python 3.6.6</p>
  
  <p>This code does not work:</p>
  
  <pre><code>from datetime import date
  print(f'Updated {date.today().strftime('%m/%d/%Y')}')
  
    File "&lt;stdin&gt;", line 1
      print(f'Updated {date.today().strftime('%m/%d/%Y')}')
                                                 ^
  SyntaxError: invalid syntax
  </code></pre>
  
  <p>However, this (functionally the same) does work:</p>
  
  <pre><code>from datetime import date
  d = date.today().strftime('%m/%d/%Y')
  print(f'Updated {d}')
  
  Updated 11/12/2018
  </code></pre>
  
  <p>I feel like I'm probably missing something obvious, and am fine with the second iteration, but I want to understand what's happening here.</p>