Fix encoding issues related to Python 3 upgrade.

Python 3 str() is a unicode already, so can't be decoded.
subprocess.Popen needs to be in text mode (universal_newlines is the
oldest compatible kwarg for this) in order to do line-based buffering.
In general, all the filesystem encoding stuff we were doing is done by
Python itself now.

zenmap/radialnet/gui/SaveDialog.py

@@ -83,7 +83,7 @@ for type in TYPES:
         EXTENSIONS[type[2]] = type[1]
 
 
-class SaveDialog(zenmapGUI.FileChoosers.UnicodeFileChooserDialog):
+class SaveDialog(Gtk.FileChooserDialog):
     def __init__(self):
         """
         """