docs: def on_modified(self, event, dry_run=False, remove_uploaded=True):
          'Called when a file (or directory) is modified. '
          super(ArchiveEventHandler, self).on_modified(event)
          src_path = event.src_path
          if event.is_directory:
              if not platform.is_darwin():
                  log.info("event is a directory, safe to ignore")
                  return
              # OSX is behaving erratically and we need to paper over it.
              # the OS only reports every other file event,
              # but always fires off a directory event when a file has changed. (OSX 10.9 tested)
              # so we need to find the actual file changed and then go on from there
              files = [event.src_path+"/"+f for f in os.listdir(event.src_path)]
              try:
                  src_path = max(files, key=os.path.getmtime)
              except (OSError, ValueError) as e: # broken symlink or directory empty
                  return
          log.info('Modified file detectd: %s', src_path)
          #
          # we're receiving events at least two times: on file open and on file close.
          # OSes might report even more
          # we're only interested in files that are closed (finished), so we try to
          # open it. if it is locked, we can infer that someone is still writing to it.
          # this works on platforms: windows, ... ?
          # TODO: investigate http://stackoverflow.com/a/3876461 for POSIX support
          try:
              open(src_path)   # win exclusively
              os.open(src_path, os.O_EXLOCK) # osx exclusively
          except IOError: # file is not finished
              log.info('File is not finished')
              return
          except AttributeError: # no suuport for O_EXLOCK (only BSD)
              pass
          return self._new(src_path, dry_run, remove_uploaded)