Handling invalid URL scheme

[karlcow]

When accessing speedtest.net with an Android mobile user agent, the site decides to redirect automatically to the mobile application store.

market://speedtest.net

This would not work. We have to test that the uri has a valid scheme before trying to access the resource.

Traceback (most recent call last):
  File "survey/core.py", line 319, in <module>
    main()
  File "survey/core.py", line 271, in main
    htmltext, finaluri = req.getContent(uri, UAREF)
  File "survey/core.py", line 68, in getContent
    r = requests.get(uri, headers=headers)
  File "/Library/Python/2.7/site-packages/requests/api.py", line 54, in get
    return request('get', url, **kwargs)
  File "/Library/Python/2.7/site-packages/requests/safe_mode.py", line 37, in wrapped
    return function(method, url, **kwargs)
  File "/Library/Python/2.7/site-packages/requests/api.py", line 42, in request
    return s.request(method=method, url=url, **kwargs)
  File "/Library/Python/2.7/site-packages/requests/sessions.py", line 230, in request
    r.send(prefetch=prefetch)
  File "/Library/Python/2.7/site-packages/requests/models.py", line 609, in send
    self._build_response(r)
  File "/Library/Python/2.7/site-packages/requests/models.py", line 296, in _build_response
    request.send()
  File "/Library/Python/2.7/site-packages/requests/models.py", line 465, in send
    url = self.full_url
  File "/Library/Python/2.7/site-packages/requests/models.py", line 377, in full_url
    raise InvalidSchema("Invalid scheme %r" % scheme)
requests.exceptions.InvalidSchema: Invalid scheme 'market'