Report error data on failed connection responses.

lib/services/connections_manager.dart

@@ -54,7 +54,7 @@ class ConnectionsManager extends ChangeNotifier {
         notifyListeners();
       },
       onError: (error) {
-        _logger.severe('Error following ${connection.name}');
+        _logger.severe('Error following ${connection.name}: $error');
       },
     );
   }
@@ -73,7 +73,7 @@ class ConnectionsManager extends ChangeNotifier {
         notifyListeners();
       },
       onError: (error) {
-        _logger.severe('Error following ${connection.name}');
+        _logger.severe('Error following ${connection.name}: $error');
       },
     );
   }