Add Exceptions

server/app/exceptions.py

@@ -0,0 +1,14 @@
+class TrackExistsInPlaylist(Exception):
+    """
+    Exception raised when a track is already in a playlist.
+    """
+
+    pass
+
+
+class PlaylistExists(Exception):
+    """
+    Exception raised when a playlist already exists.
+    """
+
+    pass