old_contents: """FreeBSD port building infrastructure."""
  
  from __future__ import absolute_import
  
  from . import event
  
  def stop(kill=False, kill_clean=False):
    """Stop building ports and cleanup."""
    from os import killpg
    from signal import SIGTERM, SIGKILL
    from .builder import builders
    from .env import cpus, flags
    from .queue import attr_queue, clean_queue, queues
    from .subprocess import children
  
    if flags["no_op"]:
      exit(254)
  
    flags["mode"] = "clean"
  
    if kill_clean:
      cleaning = ()
    else:
      cleaning = set(i.pid for i in clean_queue.active)
  
    # Kill all active children
    for pid in children():
      if pid not in cleaning:
        try:
          killpg(pid, SIGKILL if kill else SIGTERM)
        except OSError:
          pass
  
    # Stop all queues
    attr_queue.load = 0
    for queue in queues:
      queue.load = 0
  
    # Make cleaning go a bit faster
    if kill_clean:
      clean_queue.load = 0
      return
    else:
      clean_queue.load = cpus
  
    # Wait for all active ports to finish so that they may be cleaned
    active = set()
    for queue in queues:
      for job in queue.active:
        port = job.port
        active.add(port)
        port.stage_completed.connect(lambda x: x.clean())
  
    # Clean all other outstanding ports
    for builder in builders:
      for port in builder.ports:
        if port not in active:
          port.clean()
  
new_contents: """FreeBSD port building infrastructure."""
  
  from __future__ import absolute_import
  
  from . import event
  
  def stop(kill=False, kill_clean=False):
    """Stop building ports and cleanup."""
    from os import killpg
    from signal import SIGTERM, SIGKILL
    from .builder import builders
    from .env import cpus, flags
    from .queue import attr_queue, clean_queue, queues
    from .subprocess import children
  
    if flags["no_op"]:
      raise SystemExit(254)
  
    flags["mode"] = "clean"
  
    if kill_clean:
      cleaning = ()
    else:
      cleaning = set(i.pid for i in clean_queue.active)
  
    # Kill all active children
    for pid in children():
      if pid not in cleaning:
        try:
          killpg(pid, SIGKILL if kill else SIGTERM)
        except OSError:
          pass
  
    # Stop all queues
    attr_queue.load = 0
    for queue in queues:
      queue.load = 0
  
    # Make cleaning go a bit faster
    if kill_clean:
      clean_queue.load = 0
      return
    else:
      clean_queue.load = cpus
  
    # Wait for all active ports to finish so that they may be cleaned
    active = set()
    for queue in queues:
      for job in queue.active:
        port = job.port
        active.add(port)
        port.stage_completed.connect(lambda x: x.clean())
  
    # Clean all other outstanding ports
    for builder in builders:
      for port in builder.ports:
        if port not in active:
          port.clean()
  
subject: Use SystemExit, not exit() to initiate a shutdown.