Removed IllegalAccessException and UnsupportedOperationException.

utils/archive/entry.dart

Index: utils/archive/entry.dart
diff --git a/utils/archive/entry.dart b/utils/archive/entry.dart
index b5a97d1e74f0c1aaa29ff7ce85d8227994e844b7..e65b9658e5acd16f97ccf06480da21ebc62b09ba 100644
--- a/utils/archive/entry.dart
+++ b/utils/archive/entry.dart
@@ -260,10 +260,10 @@ class ArchiveEntry {
    */
   InputStream openInputStream() {
     if (_archiveId == null) {
-      throw new UnsupportedOperationException("Cannot open input stream for "
+      throw new UnsupportedError("Cannot open input stream for "
           "archive entry $pathname.");
     } else if (_input != null) {
-      throw new UnsupportedOperationException("An input stream has already been"
+      throw new UnsupportedError("An input stream has already been"
           "opened for archive entry $pathname.");
     }