public ByteArrayOutputStream getStream() {
      return stream;
    }
Instantiate a WriterAppender and set the output destination to a
new {@link OutputStreamWriter} initialized with <code>os</code>
as its {@link OutputStream}.

@param name             The name of the Appender.
@param layout           The layout to format the message.
@param filter
@param ignoreExceptions
@param immediateFlush
@param manager          The OutputStreamManager.
ql/src/test/org/apache/hadoop/hive/ql/metadata/StringAppender.java