Revision 1914679

class DifflibDiffContent does not work, and maybe never did. There is
no .next() method on the unified_diff() result object. While it would
be possible to use the next() function, it is better to just remove
this entirely and require the host OS to have a diff executable (not a
hard requirement).

* tools/hook-scripts/mailer/mailer.py:
  (DiffGenerator.__getitem__): remove OSError exception, as the diff
    executable must be present.
  (class DifflibDiffContent): removed.