title: Iterable unpacking and slice assignment
body: <pre><code>L = [0, 1, 2]
  L[::2], *rest = "abcdef"
  print(L, rest)
  </code></pre>
  
  <p>Expected output:</p>
  
  <pre><code>['a', 1, 'b'] ['c', 'd', 'e', 'f']
  </code></pre>
  
  <p>Actual output:</p>
  
  <pre><code>ValueError: attempt to assign sequence of size 1 to extended slice of size 2
  </code></pre>
  
  <p>Is using unpacking assignment in combination with extended slice assignment not possible for some reason? Why? I don't see anything obvious in <a href="https://www.python.org/dev/peps/pep-3132/" rel="nofollow noreferrer">PEP 3132 -- Extended Iterable Unpacking</a> or in the Python datamodel suggesting this shouldn't be valid.</p>