Also seen when installing for example graphite-carbon. Typical traceback:

>   File "/usr/lib/python2.7/dist-packages/carbon/service.py", line 18, in <module>
>     from twisted.application.internet import TCPServer, TCPClient, UDPServer
>   File "/usr/lib/python2.7/dist-packages/twisted/application/internet.py", line 54, in <module>
>     from automat import MethodicalMachine
>   File "/usr/lib/python2.7/dist-packages/automat/__init__.py", line 2, in <module>
>     from ._methodical import MethodicalMachine
>   File "/usr/lib/python2.7/dist-packages/automat/_methodical.py", line 34, in <module>
>     @attr.s(frozen=True)
> exceptions.TypeError: attributes() got an unexpected keyword argument 'frozen'

The root cause seems to be one step away from Twisted: python-twisted-code 17.9.0 depends python-automat>=0.6.0 depends python-attr, it's the latter which is broken. Twisted 16.x from xenial doesn't depend on automat at all, hence it escapes.

https://github.com/glyph/automat/issues/65 describes the issue:
> The patch for #62 in 3766391 that passes the frozen keyword to attr.s assumes attrs>=16.1.0 per python-attrs/attrs@cfa6d2e.

The initial patch for #62 made it into automat-0.6.0 (a year ago) but the fix in https://github.com/glyph/automat/pull/66 didn't, and there's been no point release since: https://github.com/glyph/automat/releases

My local workaround for now has been to downgrade Twisted to 16.0.0-1ubuntu0.2 (from xenial repo) and hold them.