GNU Radio 3.8 support

https://wiki.gnuradio.org/index.php/GNU_Radio_3.8_OOT_Module_Porting_Guide

Change-Id: I23dd638c8c48ed0a4b50559ce33fbd5e60b7dcbc
diff --git a/docs/doxygen/doxyxml/text.py b/docs/doxygen/doxyxml/text.py
index 629edd1..9cb7b4d 100644
--- a/docs/doxygen/doxyxml/text.py
+++ b/docs/doxygen/doxyxml/text.py
@@ -1,7 +1,8 @@
 #
 # Copyright 2010 Free Software Foundation, Inc.
 #
-# This file is part of GNU Radio
+# This file was generated by gr_modtool, a tool from the GNU Radio framework
+# This file is a part of gr-gsm
 #
 # GNU Radio is free software; you can redistribute it and/or modify
 # it under the terms of the GNU General Public License as published by
@@ -21,12 +22,13 @@
 """
 Utilities for extracting text from generated classes.
 """
+from __future__ import unicode_literals
 
 def is_string(txt):
     if isinstance(txt, str):
         return True
     try:
-        if isinstance(txt, unicode):
+        if isinstance(txt, str):
             return True
     except NameError:
         pass
@@ -49,7 +51,7 @@
     elif is_string(obj):
         return obj
     else:
-        raise StandardError('Expecting a string or something with content, content_ or value attribute')
+        raise Exception('Expecting a string or something with content, content_ or value attribute')
     # If this bit is a paragraph then add one some line breaks.
     if hasattr(obj, 'name') and obj.name == 'para':
         result += "\n\n"