Break up another large file

pkg/analyzer/lib/src/error/pending_error.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 analyzer.src.error.pending_error;
 
 import 'package:analyzer/dart/ast/ast.dart';
 import 'package:analyzer/dart/element/element.dart';
+import 'package:analyzer/error/error.dart';
+import 'package:analyzer/src/error/codes.dart';
 import 'package:analyzer/src/generated/constant.dart';
-import 'package:analyzer/src/generated/error.dart';
 import 'package:analyzer/src/generated/source.dart';
 
 /**
  * A pending error is an analysis error that could not be reported at the time
  * it was discovered because some piece of information might be missing. After
  * the information has been computed, the pending error can be converted into a
  * real error.
  */
 abstract class PendingError {
   /**
@@ skipping 51 matching lines @@
     if (reason != null) {
       errorCode = HintCode.MISSING_REQUIRED_PARAM_WITH_DETAILS;
       arguments = [parameterName, reason];
     } else {
       errorCode = HintCode.MISSING_REQUIRED_PARAM;
       arguments = [parameterName];
     }
     return new AnalysisError(source, offset, length, errorCode, arguments);
   }
 }