title: ImportError: cannot import name 'Literal' from 'typing'
body: <p>I have recently started using <a href="https://www.python.org/dev/peps/pep-0484/" rel="noreferrer">PEP 484</a> and <a href="https://www.python.org/dev/peps/pep-0586/" rel="noreferrer">PEP 586</a> to make my code clearer and more accessible. So far everything was ok, but when I wanted to use <code>Literal</code> from the package <code>typing</code> it appears it couldn't be imported.
  What is the most surprising is that PyCharm isn't complaining at all for importing it or using it.</p>
  
  <p>The code I want to use in the end is looking like that :</p>
  
  <pre class="lang-py prettyprint-override"><code>SomeVar = TypeVar("SomeVar", Literal['choice1'], Literal['choice2'], someType)
  </code></pre>
  
  <p>It would be used in the cases where you can have a string to describe what you want or an already made solution e.g :</p>
  
  <pre class="lang-py prettyprint-override"><code>def someFunc(my_var: SomeVar = 'choice1'):
      result = []
      if my_var == 'choice1':
          result.append(...)
      else:
          result = my_var
      return result
  </code></pre>
  
  <p>I use an Anaconda environment with Python 3.7.7.</p>