Not a bug in Unity. libatspi2.0-0 should have Breaks: and Replaces: control fields in the debian/control file which ensure that libatspi1.0-0 is removed on upgrade.
Not a bug in Unity. libatspi2.0-0 should have Breaks: and Replaces: control fields in the debian/control file which ensure that libatspi1.0-0 is removed on upgrade.