Find exact with no hits test and impl.

mopidy/backends/gstreamer.py

@@ -199,3 +199,6 @@ class GStreamerLibraryController(BaseLibraryController):
             return self._uri_mapping[uri]
         except KeyError:
             raise LookupError
+
+    def find_exact(self, type, query):
+        return Playlist()

tests/backends/base.py

@@ -1011,7 +1011,8 @@ class BaseLibraryControllerTest(object):
         self.assertRaises(LookupError, test)
 
     def test_find_exact_no_hits(self):
-        raise SkipTest
+        result = self.library.find_exact('track', 'unknown track')
+        self.assertEqual(result, Playlist())
 
     def test_find_exact_artist(self):
         raise SkipTest