private static IllegalArgumentException unexpectedHeader(byte header) {
    throw new IllegalArgumentException(
      "unexpected value in first byte: 0x" + Long.toHexString(header));
  }
Creates the standard exception when the encoded header byte is unexpected for the decoding
context.
@param header value used in error message.
hbase-common/src/main/java/org/apache/hadoop/hbase/util/OrderedBytes.java