0.49 Upgrade Error

Performing a standard upgrade from 0.47. Using Raspbian virtualenv installation i get the following error:

(homeassistant) homeassistant@homepi:~/.homeassistant $ pip3 install --upgrade homeassistant
Collecting homeassistant
  Using cached homeassistant-0.49.0-py2.py3-none-any.whl
Requirement already up-to-date: requests==2.14.2 in /srv/homeassistant/lib/python3.4/site-packages (from homeassistant)
Requirement already up-to-date: pytz>=2017.02 in /srv/homeassistant/lib/python3.4/site-packages (from homeassistant)
Requirement already up-to-date: pip>=7.1.0 in /srv/homeassistant/lib/python3.4/site-packages (from homeassistant)
Requirement already up-to-date: async-timeout==1.2.1 in /srv/homeassistant/lib/python3.4/site-packages (from homeassistant)
Collecting chardet==3.0.4 (from homeassistant)
  Using cached chardet-3.0.4-py2.py3-none-any.whl
Requirement already up-to-date: voluptuous==0.10.5 in /srv/homeassistant/lib/python3.4/site-packages (from homeassistant)
Requirement already up-to-date: jinja2>=2.9.5 in /srv/homeassistant/lib/python3.4/site-packages (from homeassistant)
Collecting aiohttp==2.2.3 (from homeassistant)
Exception:
Traceback (most recent call last):
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/basecommand.py", line 215, in main
    status = self.run(options, args)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/commands/install.py", line 324, in run
    requirement_set.prepare_files(finder)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/req/req_set.py", line 380, in prepare_files
    ignore_dependencies=self.ignore_dependencies))
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/req/req_set.py", line 554, in _prepare_file
    require_hashes
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/req/req_install.py", line 278, in populate_link
    self.link = finder.find_requirement(self, upgrade)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/index.py", line 465, in find_requirement
    all_candidates = self.find_all_candidates(req.name)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/index.py", line 423, in find_all_candidates
    for page in self._get_pages(url_locations, project_name):
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/index.py", line 568, in _get_pages
    page = self._get_page(location)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/index.py", line 683, in _get_page
    return HTMLPage.get_page(link, session=self.session)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/index.py", line 792, in get_page
    "Cache-Control": "max-age=600",
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/_vendor/requests/sessions.py", line 488, in get
    return self.request('GET', url, **kwargs)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/download.py", line 386, in request
    return super(PipSession, self).request(method, url, *args, **kwargs)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/_vendor/requests/sessions.py", line 475, in request
    resp = self.send(prep, **send_kwargs)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/_vendor/requests/sessions.py", line 596, in send
    r = adapter.send(request, **kwargs)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/_vendor/cachecontrol/adapter.py", line 37, in send
    cached_response = self.controller.cached_request(request)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/_vendor/cachecontrol/controller.py", line 111, in cached_request
    resp = self.serializer.loads(request, cache_data)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/_vendor/cachecontrol/serialize.py", line 114, in loads
    return getattr(self, "_loads_v{0}".format(ver))(request, data)
  File "/srv/homeassistant/lib/python3.4/site-packages/pip/_vendor/cachecontrol/serialize.py", line 176, in _loads_v2
    cached = json.loads(zlib.decompress(data).decode("utf8"))
zlib.error: Error -3 while decompressing data: incorrect data check

Any help appreciated