Make core.uri_schemes include URI schemes from all backends

mopidy/core/actor.py

@@ -43,7 +43,10 @@ class Core(pykka.ThreadingActor, AudioListener):
     @property
     def uri_schemes(self):
         """List of URI schemes we can handle"""
-        return self._backends[0].uri_schemes.get()
+        futures = [backend.uri_schemes for backend in self._backends]
+        results = pykka.get_all(futures)
+        schemes = [uri_scheme for result in results for uri_scheme in result]
+        return sorted(schemes)
 
     def reached_end_of_stream(self):
         self.playback.on_end_of_track()

tests/core/actor_test.py

@@ -0,0 +1,26 @@
+import mock
+import pykka
+
+from mopidy.core import Core
+
+from tests import unittest
+
+
+class CoreActorTest(unittest.TestCase):
+    def setUp(self):
+        self.backend1 = mock.Mock()
+        self.backend1.uri_schemes.get.return_value = ['dummy1']
+
+        self.backend2 = mock.Mock()
+        self.backend2.uri_schemes.get.return_value = ['dummy2']
+
+        self.core = Core(audio=None, backends=[self.backend1, self.backend2])
+
+    def tearDown(self):
+        pykka.ActorRegistry.stop_all()
+
+    def test_uri_schemes_has_uris_from_all_backends(self):
+        result = self.core.uri_schemes
+
+        self.assertIn('dummy1', result)
+        self.assertIn('dummy2', result)