lldb package missing python-six dependency

[Nicholas Devenish]

Xenial 16.04.3 on fresh VM, and also exhibited via docker image for 16.04.3.

$ apt-cache policy lldb
lldb:
  Installed: 1:3.8-33ubuntu3.1
  Candidate: 1:3.8-33ubuntu3.1
  Version table:
 *** 1:3.8-33ubuntu3.1 500
        500 http://archive.ubuntu.com/ubuntu xenial-updates/universe amd64 Packages
        100 /var/lib/dpkg/status
     1:3.8-33ubuntu3 500
        500 http://archive.ubuntu.com/ubuntu xenial/universe amd64 Packages

Expected:
  No error on launching

What happens:
  $ sudo apt-get update
  $ sudo apt-get install lldb
  <...>

  $ lldb
  Traceback (most recent call last):
    File "<string>", line 1, in <module>
    File "/usr/lib/python2.7/dist-packages/lldb/__init__.py", line 123, in <module>
      import six
  ImportError: No module named six

Solved for me by:
  $ sudo apt-get install python-six
  $ lldb
  (lldb)