Revision 1914913

Switch to boolean return values for .generate() rather than an exit
code. Map the bool to an exit code for sys.exit()

* tools/hook-scripts/mailer/mailer.py:
  (Commit.generate): return FAILED as its existing boolean value
  (PropChange.generate): return FAILED as its existing boolean value
  (Lock.generate): return FAILED as its existing boolean value
  (__main__): use FAILED for the return value, update sys.exit()