2to3: preparatory work for python 3

[cvubrugier]

This patch for configshell-fb intend to ease compatibility with Python 3.

I ran 2to3 and selected the only fix named except that we can apply right now because it is compatible with Python 2.7.

I did not apply the other fixes because I think they will break compatibility with Python 2.7. For configshell-fb, these fixes are:

• basestring
• dict
• import
• imports
• raw_input
• unicode
• xrange
• zip