Log more information for the connection failure

lib/datasource.js

@@ -233,7 +233,7 @@ DataSource.prototype.setup = function(name, settings) {
                 this.emit('connected');
             } else {
                 // The connection fails, let's report it and hope it will be recovered in the next call
-                console.error(err);
+                console.error('Connection fails: ', err, '\nIt will be retried for the next request.');
                 this.connecting = false;
             }