Canary is an app that is essentially an alternate front end to Splunk.  It implements its own extensible user interface and dashboarding system that other apps can use.   
Since it is backwards compatible to a subset of the "Sideview XML" views that you might have created with Sideview Utils, it offers a path for existing Sideview Utils content to potentially continue running even in Splunk 8, 9 and beyond.
  
It is a descendant of Sideview Utils but whereas Sideview Utils ran on top of Splunk’s “Advanced XML” systems, Canary does not.
For a great deal more information about Canary, see our website ( https://sideviewapps.com/documentation/canary )

NOTE: This app runs in python3 without any problems and without any changes required.  Splunk's "Upgrade Readiness App" may erroneously state that our apps do not run in python3 but it is wrong and we have been working with Splunk to try and get them to address this.