pylint #18949 checker for string formatting [resolved]

See http://lists.logilab.org/pipermail/python-projects/2009-November/002086.html and http://lists.logilab.org/pipermail/python-projects/2009-November/002111.html

prioritynormal
typeenhancement
done in0.19.0
load0.300
load left0.000
closed by<not specified>