Both an existing raspberry pi 3 assistant-sdk setup and a freshly created one are producing identical errors at all times idle or otherwise.  The lines below are repeating over and do not seem to be affected by the state of the assistant.  Replicates across multiple developer accounts, devices and projects.  Present with both the stock hotword example and modified scripts that worked previously.  All cases are library assistant and python 3 on raspberry pi 3 model B running raspbian stretch.

[9780:9796:ERROR:assistant_ssdp_client.cc(210)] Failed to parse
  header: LOCATION: about:blank
[9780:9796:ERROR:assistant_ssdp_client.cc(76)] LOCATION header doesn't
  contain a valid url
This fixed it for me: pip3 install google-assistant-library==0.1.0
Assistant SDK on raspberry pi 3 throwing repeated location header errors