stream: Add scheme and blacklist check to translate_uri

We don't bother with this inside the unwrap code as if something redirects us
so be it.

mopidy/stream/actor.py

@@ -74,6 +74,13 @@ class StreamLibraryProvider(backend.LibraryProvider):
 class StreamPlaybackProvider(backend.PlaybackProvider):
 
     def translate_uri(self, uri):
+        if urllib.parse.urlsplit(uri).scheme not in self.backend.uri_schemes:
+            return None
+
+        if self.backend._blacklist_re.match(uri):
+            logger.debug('URI matched metadata lookup blacklist: %s', uri)
+            return uri
+
         return _unwrap_stream(
             uri,
             timeout=self.backend._timeout,

tests/stream/test_playback.py

@@ -30,7 +30,7 @@ def config():
         'stream': {
             'timeout': TIMEOUT,
             'metadata_blacklist': [],
-            'protocols': ['file'],
+            'protocols': ['http'],
         },
         'file': {
             'enabled': False