title: Scope ID in python ipaddress.IPv6Address instances
body: <p>I'm currently writing a python wrapper for a C++-Library that does network communication via IPv6 link-local addresses. To initialize the library the network interface has to be selected. This is done via the link-local address of the desired interface.</p>
  
  <p>On the C++ side we use boost <a href="http://www.boost.org/doc/libs/1_57_0/doc/html/boost_asio/reference/ip__address_v6.html" rel="nofollow">address_v6 objects</a>. On the python side the <a href="https://docs.python.org/3/library/ipaddress.html#ipaddress.IPv6Address" rel="nofollow">ipaddress.IPv6Address</a> seemed to be a perfect match.</p>
  
  <p>However I did not find a way to specify the scope id of the interface on the python side. </p>
  
  <pre><code>ip = ipaddress.IPv6Address('fe80::3c4e:6a7:3f57:4cbc%12')
  </code></pre>
  
  <p>gives the error:</p>
  
  <pre><code>Traceback (most recent call last):
    File "&lt;stdin&gt;", line 1, in &lt;module&gt;
    File "C:\Python34\lib\ipaddress.py", line 1835, in __init__
      self._ip = self._ip_int_from_string(addr_str)
    File "C:\Python34\lib\ipaddress.py", line 1664, in _ip_int_from_string
      raise AddressValueError("%s in %r" % (exc, ip_str)) from None
  ipaddress.AddressValueError: Only hex digits permitted in '4cbc%12' in 'fe80::3c4e:6a7:3f57:4cbc%12'
  </code></pre>
  
  <p>IPv6 link-local communication is pretty much impossible without the scope ids. </p>
  
  <p>Am I missing something here or is the best way to specify an IPv6 link-local interface addresses as a string?</p>