Some modules (httplib, StringIO, ...) were renamed in python3. This
patch try to import the proper symbols from python3 and then fallback to
python2 in a case ImportError will appear.
There is one exception, python 2.7 got the io module with StringIO, but
it allow unicode arguments only. Therefor the old module is poked before
new one.
* util/packagequery.py: it's used to query a RPM or DEB package. It also contains a
base class for all package types (PackageQuery())
* util/debquery.py: query a DEB package (name, version, release, provides, requires etc.)
- adapted util/rpmquery.py to use PackageQuery() as a base class
- minor changes in util/ar.py
