[PyQt] Inconsistent behavior of PyQt5 QSciLexerCustom constructor across platforms

[Dominique Cyprès]

After a recent update of my system to Xubuntu 12.10, I have noticed 
unusual behavior in the QSciLexerCustom constructor for PyQt5. Some 
simple example code for the class:

http://pastebin.com/kXC3eW1Q

worked just fine before the update, and continues to work fine on a 
Windows XP VM using PyQt GPL v5.3.2 for Python v3.4, but now produces 
the following traceback on my primary development system:

Traceback (most recent call last):
   File "lexer.py", line 105, in <module>
     win = MainWindow()
   File "lexer.py", line 19, in __init__
     self.lexer = CustomLexer(self.editor)
   File "lexer.py", line 26, in __init__
     Qsci.QsciLexerCustom.__init__(self, parent)
TypeError: QsciLexerCustom(QObject parent=None): argument 1 has 
unexpected type 'QsciScintilla'

My package manager reports the PyQt5 version as 5.3.2+dfsg-1ubuntu1 and 
the PyQt5.Qsci version as 2.8.3+dfsg-3. Both are the latest available 
version available from the distro repository. I'm not sure if this is a 
problem with packaging, something non-standard in the code I'm running, 
or something else.

Thank you for your attention,
Dominique