Delint test_sftp (remove unused imports and unused variables, remove excess whitespace, move imports to top, remove semicolon terminator)

--HG--
extra : source : 01df712a396de5fa7e1c0cc265411fdb2bbc5f41
Adding test capturing desired behavior and demonstrating issue #142.
Remove 'file_size' check from tests. The docstring indicates this parameter is to be passed to the callback, and there's no reason to think this parameter is relevant in affecting whether a useful stat object has been passed (especially when the 'confirm' parameter is explicitly supplied for that decision. This fixes #142.
Update NEWS per #142
Merge branch '1.10' into 143-int
Dumb format tweak to NEWS