remove dependencies to analyzer from lib/src/fasta

pkg/front_end/lib/src/fasta/testing/environment_variable.dart

 // Copyright (c) 2016, 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 fasta.environment_variable;
+library fasta.testing.environment_variable;
 
 import 'dart:async' show Future;
 
 import 'dart:io' show Directory, File, Platform;
 
-import 'errors.dart' show inputError;
+import '../errors.dart' show inputError;
 
 class EnvironmentVariable {
   final String name;
 
   final String what;
 
   const EnvironmentVariable(this.name, this.what);
 
   Future<String> get value async {
     String value = Platform.environment[name];
@@ skipping 41 matching lines @@
         null,
         null,
         "The environment variable '$name' has the value "
         "'$value', that isn't a directory. $what");
   }
 }
 
 Future<bool> fileExists(Uri base, String path) async {
   return await new File.fromUri(base.resolve(path)).exists();
 }