Merge lp:~ed.so/duplicity/duplicity.helpfix into lp:duplicity/0.6

[edso]

ix rare 'TypeError: encode() argument 1 must be string, not None'
read here
http://lists.nongnu.org/archive/html/duplicity-talk/2012-09/msg00016.html

=== modified file 'duplicity/commandline.py'
--- duplicity/commandline.py	2012-05-16 11:03:20 +0000
+++ duplicity/commandline.py	2012-09-10 17:58:19 +0000
@@ -181,11 +181,11 @@
 class OPHelpFix(optparse.OptionParser):
     def _get_encoding(self, file):
         """
-        try to get the encoding or switch to UTF-8
+        try to get the encoding or use UTF-8
         which is default encoding in python3 and most recent unixes
         """
-        encoding = getattr(file, "encoding", "UTF-8")
-        return encoding
+        encoding = getattr(file, "encoding", None)
+        return encoding if encoding else 'utf-8'
 
     def print_help(self, file=None):
         """