message: python: restore sys.path in bootstrap()
  multiprocessing need to start from bootstrap code
  loading may fail due to missing os.add_dll_directory() calls
diff: @@ -18,6 +18,10 @@ except ImportError:
  def bootstrap():
  import sys
  +
  + import copy
  + save_sys_path = copy.copy(sys.path)
  +
  if hasattr(sys, 'OpenCV_LOADER'):
  print(sys.path)
  raise ImportError('ERROR: recursion is detected during loading of "cv2" binary extensions. Check OpenCV installation.')
  @@ -85,6 +89,8 @@ def bootstrap():
  del sys.modules['cv2']
  import cv2
  + sys.path = save_sys_path # multiprocessing should start from bootstrap code (https://github.com/opencv/opencv/issues/18502)
  +
  try:
  import sys
  del sys.OpenCV_LOADER
  