Add check for text file encodings

pre_commit_hooks/check_encoding.py

@@ -0,0 +1,29 @@
+import argparse
+from typing import Optional
+from typing import Sequence
+
+
+def main(argv: Optional[Sequence[str]] = None) -> int:
+    parser = argparse.ArgumentParser()
+    parser.add_argument('filenames', nargs='*', help='Filenames to check.')
+    parser.add_argument('--encoding', help='Encoding to assert.')
+    args = parser.parse_args(argv)
+
+    retval = 0
+    for filename in args.filenames:
+        try:
+            with open(filename, encoding=args.encoding) as f:
+                f.read()
+        except LookupError as exc:
+            # Unknown encoding, don't bother with the rest
+            print(f'{__file__}: {exc}')
+            retval = 2
+            break
+        except Exception as exc:
+            print(f'{filename}: {exc}')
+            retval = 1
+    return retval
+
+
+if __name__ == '__main__':
+    raise SystemExit(main())