Fix analyzer hints and warnings in test/.

test/io_test.dart

 // Copyright (c) 2012, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 library io_test;
 
 import 'dart:async';
 import 'dart:io';
 
 import 'package:path/path.dart' as path;
 import 'package:pub/src/io.dart';
 import 'package:test/test.dart';
 
-import 'test_pub.dart';
-
 main() {
   group('listDir', () {
     test('ignores hidden files by default', () {
       expect(withTempDir((temp) {
         writeTextFile(path.join(temp, 'file1.txt'), '');
         writeTextFile(path.join(temp, 'file2.txt'), '');
         writeTextFile(path.join(temp, '.file3.txt'), '');
         createDir(path.join(temp, '.subdir'));
         writeTextFile(path.join(temp, '.subdir', 'file3.txt'), '');
 
@@ skipping 328 matching lines @@
           expect(predicate(symlink2Path), equals(forMultiLevelFileSymlink));
         }), completes);
       });
     }
   });
 }
 
 /// Like [withTempDir], but canonicalizes the path before passing it to [fn].
 Future withCanonicalTempDir(Future fn(String path)) =>
   withTempDir((temp) => fn(canonicalize(temp)));