Revision 1914681

Switch from a generator class/object to a simple generation function.

* tools/hook-scripts/mailer/mailer.py:
  (generate_content): use new function, rather than the old
    DiffGenerator class.
  (class DiffGenerator): remove, but keep its contents as close as
    possible for new function ...
  (generate_changelist_diffs): ... here. This creates a "self" object
    to hold "instance vars" as if it was still the old class. This
    minimizes the changes necessary: switch from raising IndexError to
    just returning; switch from returning values to yield