CI check comments of cheanged Python files

check_comment_ascii.py

@@ -0,0 +1,36 @@
+#!/usr/bin/env python3
+import sys
+import tokenize
+import ast
+import pathlib
+import re
+
+ASCII = re.compile(r"^[ -~]*\Z")  # Only printable ASCII
+
+
+def check(src: str, name: str) -> int:
+    """
+    I'm a docstring
+    """
+    ok = 1
+    # A common comment begins with `#`
+    with tokenize.open(src) as fp:
+        for tk in tokenize.generate_tokens(fp.readline):
+            if tk.type == tokenize.COMMENT and not ASCII.fullmatch(tk.string):
+                print(f"{name}:{tk.start[0]}: non-ASCII comment: {tk.string}")
+                ok = 0
+    # A docstring begins and ends with `'''`
+    for node in ast.walk(ast.parse(pathlib.Path(src).read_text(), filename=name)):
+        if isinstance(node, (ast.FunctionDef, ast.ClassDef, ast.Module)):
+            if (doc := ast.get_docstring(node)) and not ASCII.fullmatch(doc):
+                print(f"{name}:{node.lineno}: non-ASCII docstring: {doc}")
+                ok = 0
+    return ok
+
+
+if __name__ == "__main__":
+    status = 0
+    for file in sys.argv[1:]:
+        if not check(file, file):
+            status = 1
+    sys.exit(status)