style: Fix Python 2.6 compatibility
style: Fix Python 2.6 compatibility

The style checker code needs to disable autojunk when diffing source
files using Python's difflib. Support for this was only introduced in
Python 2.7, which leads to a TypeError exception on older Python
version. This changeset adds a fallback mechanism for old Python
versions.

gem5/gem5,sobercoder/gem5,SanchayanMaity/gem5,TUD-OS/gem5-dtu,powerjg/gem5-ci-test,aclifton/cpeg853-gem5,KuroeKurose/gem5,HwisooSo/gemV-update,qizenguf/MLC-STT,HwisooSo/gemV-update,briancoutinho0905/2dsampling,powerjg/gem5-ci-test,powerjg/gem5-ci-test,SanchayanMaity/gem5,gem5/gem5,gedare/gem5,SanchayanMaity/gem5,gedare/gem5,SanchayanMaity/gem5,gem5/gem5,cancro7/gem5,sobercoder/gem5,Weil0ng/gem5,cancro7/gem5,cancro7/gem5,aclifton/cpeg853-gem5,HwisooSo/gemV-update,rallylee/gem5,sobercoder/gem5,gedare/gem5,KuroeKurose/gem5,Weil0ng/gem5,TUD-OS/gem5-dtu,rjschof/gem5,rallylee/gem5,Weil0ng/gem5,sobercoder/gem5,rjschof/gem5,briancoutinho0905/2dsampling,HwisooSo/gemV-update,rjschof/gem5,rjschof/gem5,aclifton/cpeg853-gem5,aclifton/cpeg853-gem5,KuroeKurose/gem5,SanchayanMaity/gem5,TUD-OS/gem5-dtu,cancro7/gem5,powerjg/gem5-ci-test,aclifton/cpeg853-gem5,HwisooSo/gemV-update,gem5/gem5,rallylee/gem5,rjschof/gem5,HwisooSo/gemV-update,aclifton/cpeg853-gem5,sobercoder/gem5,TUD-OS/gem5-dtu,rallylee/gem5,sobercoder/gem5,KuroeKurose/gem5,qizenguf/MLC-STT,sobercoder/gem5,powerjg/gem5-ci-test,qizenguf/MLC-STT,qizenguf/MLC-STT,briancoutinho0905/2dsampling,rallylee/gem5,KuroeKurose/gem5,TUD-OS/gem5-dtu,SanchayanMaity/gem5,gem5/gem5,gedare/gem5,aclifton/cpeg853-gem5,gedare/gem5,gem5/gem5,briancoutinho0905/2dsampling,rjschof/gem5,briancoutinho0905/2dsampling,rallylee/gem5,SanchayanMaity/gem5,cancro7/gem5,qizenguf/MLC-STT,briancoutinho0905/2dsampling,Weil0ng/gem5,KuroeKurose/gem5,TUD-OS/gem5-dtu,Weil0ng/gem5,TUD-OS/gem5-dtu,cancro7/gem5,Weil0ng/gem5,HwisooSo/gemV-update,gem5/gem5,rjschof/gem5,powerjg/gem5-ci-test,gedare/gem5,Weil0ng/gem5,KuroeKurose/gem5,briancoutinho0905/2dsampling,cancro7/gem5,gedare/gem5,powerjg/gem5-ci-test,rallylee/gem5,qizenguf/MLC-STT,qizenguf/MLC-STT