If the library of iPhoto or iTunes is stored on an external volume for example, then the folder (where the library is located) must be added to the access permissions (s. File menu). If this access permission is missing, then nothing happened after selecting iPhoto or iTunes – which is obviously not user-friendly. Now an info appears with the path that must be added to the access permissions. Where it may be recommended to add a parent folder (or even the whole external volume).
Because of problems with iTunes Connect (ITC) this version was released as 1.7.3 but is displayed as 1.7.2 in the Mac App Store (MAS).