Bad keystone responses cause InternalErrors

...in the strangest way:

Oct 6 11:52:03 openstack-host01 proxy-server: <?xml version="1.0" encoding="UTF-8"?>#015
<Error>#015
  <Code>InvalidURI</Code>#015
  <Message>Could not parse the specified URI</Message>#015
</Error>#015
:
Traceback (most recent call last):
  File "/usr/lib/python2.7/site-packages/swift3/middleware.py", line 80, in __call__
    resp = self.handle_request(req)
  File "/usr/lib/python2.7/site-packages/swift3/middleware.py", line 107, in handle_request
    res = handler(req)
  File "/usr/lib/python2.7/site-packages/swift3/controllers/obj.py", line 97, in GET
    return self.GETorHEAD(req)
  File "/usr/lib/python2.7/site-packages/swift3/controllers/obj.py", line 66, in GETorHEAD
    resp = req.get_response(self.app)
  File "/usr/lib/python2.7/site-packages/swift3/request.py", line 1075, in get_response
    headers, body, query)
  File "/usr/lib/python2.7/site-packages/swift3/request.py", line 1054, in _get_response
    raise BadSwiftRequest(err_msg)
BadSwiftRequest: <?xml version="1.0" encoding="UTF-8"?>#015
<Error>#015
  <Code>InvalidURI</Code>#015
  <Message>Could not parse the specified URI</Message>#015
</Error>#015
 (txn: tx417b5679c2284d6d80c73-0059d7a6a3)

We clearly seem to have *wanted* to return the InvalidURI message...