Fix unhandled promise rejection warnings when access token refreshing fails

lib/user-methods.js

@@ -111,7 +111,8 @@ function refreshAccessToken(user, localRealmPath, realmUrl) {
                     print_error(`Unhandled session token refresh error: could not look up session at path ${localRealmPath}`);
                 }
             }
-        });
+        })
+        .catch((e) => print_error(e));
 }
 
 /**