Use "package:" imports for pub.

test/preprocess_test.dart

Index: test/preprocess_test.dart
diff --git a/test/preprocess_test.dart b/test/preprocess_test.dart
index 4f43dd8129e0ce771ad9bc522d22c1bb907d7c3e..ac58c375d6beee289aece2d8e82c26274dfacda5 100644
--- a/test/preprocess_test.dart
+++ b/test/preprocess_test.dart
@@ -4,10 +4,10 @@
 
 library pub.test.preprocess_test;
 
+import 'package:pub/src/preprocess.dart';
 import 'package:pub_semver/pub_semver.dart';
 import 'package:unittest/unittest.dart';
 
-import '../lib/src/preprocess.dart';
 import 'test_pub.dart';
 
 main() {