$ sudo apt-get install unity-scope-tool golang git bzr python3-scope-harness mercurial
[sudo] password for steve: 
Reading package lists... Done
Building dependency tree       
Reading state information... Done
Package python3-scope-harness is not available, but is referred to by another package.
This may mean that the package is missing, has been obsoleted, or
is only available from another source

E: Package 'python3-scope-harness' has no installation candidate