Starting on Version 7.0 using the work done by others. Completely untested. I will be testing things, but I thought I'd get this base version up for others to give pull requests.

THIS IS ON THE MASTER BRANCH. The Master branch will be Python 3.0 from now on. While Python 2.7 support will not be deliberately broken, all efforts should now focus on Python 3.0 compatibility.

I can see a lot of work has been done. There's more to do. I've bumped the version number of everything I came across to the next major number for Python 3.0 compatibility indication.

Thanks everyone. I hope to update here at least once a week until we have a stable 7.0 release for calibre 5.0

Obok_plugin/utilities.py

@@ -7,21 +7,24 @@ __docformat__ = 'restructuredtext en'
 
 
 import os, struct, time
-from StringIO import StringIO
+try:
+    from StringIO import StringIO
+except ImportError:
+    from io import StringIO
 from traceback import print_exc
 
 try:
     from PyQt5.Qt import (Qt, QDialog, QPixmap, QIcon, QLabel, QHBoxLayout, QFont, QTableWidgetItem)
 except ImportError:
     from PyQt4.Qt import (Qt, QDialog, QPixmap, QIcon, QLabel, QHBoxLayout, QFont, QTableWidgetItem)
-    
+
 from calibre.utils.config import config_dir
 from calibre.constants import iswindows, DEBUG
 from calibre import prints
 from calibre.gui2 import (error_dialog, gprefs)
 from calibre.gui2.actions import menu_action_unique_name
 
-from calibre_plugins.obok_dedrm.__init__ import (PLUGIN_NAME,  
+from calibre_plugins.obok_dedrm.__init__ import (PLUGIN_NAME,
                     PLUGIN_SAFE_NAME, PLUGIN_VERSION, PLUGIN_DESCRIPTION)
 
 plugin_ID = None
@@ -39,7 +42,7 @@ else:
     def convert_qvariant(x):
         vt = x.type()
         if vt == x.String:
-            return unicode(x.toString())
+            return x.toString()
         if vt == x.List:
             return [convert_qvariant(i) for i in x.toList()]
         return x.toPyObject()
@@ -62,7 +65,7 @@ except NameError:
 def format_plural(number, possessive=False):
     '''
     Cosmetic ditty to provide the proper string formatting variable to handle singular/plural situations
-    
+
     :param: number: variable that represents the count/len of something
     '''
     if not possessive:
@@ -141,7 +144,7 @@ def showErrorDlg(errmsg, parent, trcbk=False):
     '''
     if trcbk:
         error= ''
-        f=StringIO()     
+        f=StringIO()
         print_exc(file=f)
         error_mess = f.getvalue().splitlines()
         for line in error_mess: