Rename "pathos" package to "path".

sdk/lib/_internal/pub/test/install/path/path_is_file_test.dart

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS d.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 d.file.
 
-import 'package:pathos/path.dart' as path;
+import 'package:path/path.dart' as path;
 import 'package:scheduled_test/scheduled_test.dart';
 
 import '../../descriptor.dart' as d;
 import '../../test_pub.dart';
 
 main() {
   initConfig();
   integration('path dependency when path is a file', () {
     d.dir('foo', [
       d.libDir('foo'),
       d.libPubspec('foo', '0.0.1')
     ]).create();
 
     d.file('dummy.txt', '').create();
     var dummyPath = path.join(sandboxDir, 'dummy.txt');
 
     d.dir(appPath, [
       d.pubspec({
         "name": "myapp",
         "dependencies": {
           "foo": {"path": dummyPath}
         }
       })
     ]).create();
 
     pubInstall(error: "Path dependency for package 'foo' must refer to a "
                       "directory, not a file. Was '$dummyPath'.");
   });
 }