Fixup: Return string instead of Uri object

Fixup d6728676e39a82f84bfd4fa6cf91586d16386e4f. This also worked, as
this seems to be automatically casted to a string, but better make it
explicit.
Clarify components.add_patch_camefrom_class

Fixup 19d1e181d622eff993b02cfc2624f82edd04a754