Convert some old-style string exceptions to class exceptions.
diff --git a/Lib/sunau.py b/Lib/sunau.py
index 940cfd4..5ece295 100644
--- a/Lib/sunau.py
+++ b/Lib/sunau.py
@@ -128,7 +128,8 @@
 		     AUDIO_FILE_ENCODING_LINEAR_32,
 		     AUDIO_FILE_ENCODING_ALAW_8]
 
-Error = 'sunau.Error'
+class Error(Exception):
+	pass
 
 def _read_u32(file):
 	x = 0L