Fix deprecation warnings in test_keyfile tests
Fix deprecation warnings in test_keyfile tests

In python2.6 running these tests generate a warning::

boto/tests/unit/s3/test_keyfile.py:95: DeprecationWarning: BaseException.message has been deprecated as of Python 2.6

Verified tests pass on python2.6 without any warnings.

nishigori/boto,drbild/boto,rayluo/boto,alfredodeza/boto,TiVoMaker/boto,varunarya10/boto,janslow/boto,SaranyaKarthikeyan/boto,andresriancho/boto,bryx-inc/boto,nexusz99/boto,drbild/boto,rosmo/boto,zzzirk/boto,yangchaogit/boto,nikhilraog/boto,acourtney2015/boto,disruptek/boto,alex/boto,dimdung/boto,lochiiconnectivity/boto,appneta/boto,ocadotechnology/boto,revmischa/boto,ekalosak/boto,tpodowd/boto,weebygames/boto,weka-io/boto,j-carl/boto,jotes/boto,stevenbrichards/boto,disruptek/boto,vishnugonela/boto,zachmullen/boto,vijaylbais/boto,s0enke/boto,andresriancho/boto,serviceagility/boto,dablak/boto,ramitsurana/boto,ddzialak/boto,campenberger/boto,rjschwei/boto,kouk/boto,jamesls/boto,rjschwei/boto,Pretio/boto,Timus1712/boto,kouk/boto,alex/boto,ryansb/boto,elainexmas/boto,dablak/boto,shipci/boto,jamesls/boto,jameslegg/boto,awatts/boto,felix-d/boto,bleib1dj/boto,lra/boto,darjus-amzn/boto,appneta/boto,khagler/boto,shaunbrady/boto,israelbenatar/boto,jindongh/boto,garnaat/boto,jameslegg/boto,Asana/boto,pfhayes/boto,trademob/boto,clouddocx/boto,FATruden/boto,lochiiconnectivity/boto,cyclecomputing/boto,tpodowd/boto,podhmo/boto,abridgett/boto,ric03uec/boto