Removed IllegalAccessException and UnsupportedOperationException.

lib/core/exceptions.dart

Index: lib/core/exceptions.dart
diff --git a/lib/core/exceptions.dart b/lib/core/exceptions.dart
index 12274b8c87f453042c7d480f844ee496a394ab20..c09edb592ac01bf3956a48cd0b69342a28487e53 100644
--- a/lib/core/exceptions.dart
+++ b/lib/core/exceptions.dart
@@ -34,13 +34,6 @@ class IndexOutOfRangeException implements Exception {
   final _value;
 }
 
-/**
- * Exception thrown because of attempt to modify an immutable object.
- */
-class IllegalAccessException implements Exception {
-  const IllegalAccessException();
-  String toString() => "Attempt to modify an immutable object";
-}
 
 /**
  * Exception thrown when a string or some other data does not have an expected
@@ -92,13 +85,6 @@ class EmptyQueueException implements Exception {
 }
 
 
-class UnsupportedOperationException implements Exception {
-  const UnsupportedOperationException(String this._message);
-  String toString() => "UnsupportedOperationException: $_message";
-  final String _message;
-}
-
-
 class NotImplementedException implements Exception {
   const NotImplementedException([String message]) : this._message = message;
   String toString() => (this._message !== null