Fix can_log_messages_test in pub.

sdk/lib/_internal/pub/test/transformer/can_log_messages_test.dart

Index: sdk/lib/_internal/pub/test/transformer/can_log_messages_test.dart
diff --git a/sdk/lib/_internal/pub/test/transformer/can_log_messages_test.dart b/sdk/lib/_internal/pub/test/transformer/can_log_messages_test.dart
index 3144d3206364ab9aa53d0ce33dc39ae2e07beadf..da82d5dd4dcc9ea6cd02c49740a091aacf6d6032 100644
--- a/sdk/lib/_internal/pub/test/transformer/can_log_messages_test.dart
+++ b/sdk/lib/_internal/pub/test/transformer/can_log_messages_test.dart
@@ -113,6 +113,10 @@ Warning!
       contains("ERROR"),                          // That it's an error.
     ]));
 
+    // In barback >=0.15.0, the span will point to the location where the error
+    // occurred.
+    pub.stderr.expect(allow(inOrder(["d", "^"])));
+
     pub.stderr.expect("Build failed.");
 
     pub.shouldExit(exit_codes.DATA);