test_copytree_simple(): This was leaving behind two new temp

test_copytree_simple():  This was leaving behind two new temp
directories each time it ran, at least on Windows.

Several changes:  explicitly closed all files; wrapped long
lines; stopped suppressing errors when removing a file or
directory fails (removing /shouldn't/ fail!); and changed
what appeared to be incorrect usage of os.removedirs() (that
doesn't remove empty directories at and /under/ the given
path, instead it must be given an empty leaf directory and
then deletes empty directories moving /up/ the path -- could
be that the conceptually simpler shutil.rmtree() was really
actually intended here).