no Primary/Unique constraint matching foreign constraint <str>

  Explanation:   The  foreign  relation  constraint  must  have  a
  primary  or unique constraint (with its key matching the foreign
  relation constraint's referenced  key)  defined  and  stored  or
  defined   in   the  same  relation  with  the  foreign  relation
  constraint.

  User Action:  Correct the problem and try the operation again.