text: #!/usr/bin/env python3
  import sys
  from pathlib import Path
  import itertools
  
  ROOT_DIR = Path(sys.argv[0]).resolve().parents[2]
  IMAGES_DIR = ROOT_DIR / "images"
  
  def is_ignored(f):
      return f.stem.lower() == "readme"
  
  def has_lowercase_name(f):
      return f.name.lower() == f.name.lower()
  
  IMAGE_FILE_EXTENSION_LIST = [
      ".jpg",
      ".jpeg",
      ".png",
      ".gif",
      ".webp",
      ".tiff",
      ".psd",
      ".raw",
      ".bmp",
      ".heif",
      ".indd",
      ".svg",
      ".ai",
      ".eps",
      ".pdf",
  ]
  
  def is_an_image(file_name):
      return file_name.suffix.lower() in IMAGE_FILE_EXTENSION_LIST
  
  def valid_extension(file_name):
      # Use .jpeg, not .jpg
      return file_name.suffix.lower() != ".jpg"
  
  def search_references(f_name, source_files):
      for source in source_files:
          with open(source) as fs:
              yield f_name in fs.read()
  
  def is_referenced(f, source_dir):
      return any(search_references(f.name,
                                   itertools.chain(source_dir.glob("**/*.rst"),
                                                   source_dir.glob("**/*.md"),
                                                   source_dir.glob("**/*.yaml"),
                                                   source_dir.glob("**/*.latex"),
                                                   source_dir.glob("**/*.sty"),
                                   )))
          
  fails = 0
  def fail(*msg):
      global fails
      fails += 1
      print(*msg, file=sys.stderr)
  
  if __name__ == "__main__":
  
      for f in IMAGES_DIR.glob("**/*"):
          if is_ignored(f):
              continue
  
          # nicer image name
          frel = f.relative_to(ROOT_DIR)
          if not has_lowercase_name(f):
              fail("Uppercase   ", f"{frel} is not lower-case")
          elif f.is_dir():
              continue # File-specific tests below
          elif not is_an_image(f):
              fail("Not An Image", f"{frel} is not an image file")
          elif not valid_extension(f):
              fail("Invalid Type", f"{frel} extension is invalid")
          elif not is_referenced(f, ROOT_DIR):
              fail("No Reference", f"{frel} is not referenced")
      
      if fails:
          print(f"FAIL: {fails} errors")
      else:
          print("SUCCESS")
  
      sys.exit(0 if not fails else 1)
  