title: random.choice on Enum
body: <p>I would like to use <code>random.choice</code> on an <code>Enum</code>.</p>
  
  <p>I tried:</p>
  
  <pre><code>class Foo(Enum):
      a = 0
      b = 1
      c = 2
  bar = random.choice(Foo)
  </code></pre>
  
  <p>But this code fails with a <code>KeyError</code>. How can I choose a random member of <code>Enum</code>?</p>