Convert old-style classes in Node/FS.py to new-style classes.  Refactor assignment to FS.DiskChecker.__call__.
Convert old-style classes in Node/FS.py to new-style classes.  Refactor assignment to FS.DiskChecker.__call__.

Distrotech/scons,Distrotech/scons,Distrotech/scons,Distrotech/scons,Distrotech/scons