Ran this against Drupal 8 and spotted this in it's journey

[joelpittet]

Warning: Unexpected character in input:  ' in ~/Sites/d8/convert.php on line 62

Call Stack:
    0.0014     670888   1. {main}() ~/Sites/d8/convert.php:0
    0.0027     678216   2. token_get_all() ~/Sites/d8/convert.php:62

[aaronbauman]

+1 on this with various additional information points:

Warning: Unexpected character in input: '' (ASCII=22)

Also errors for:
(ASCII=21)
(ASCII=24)
(ASCII=25)
(ASCII=26)
(ASCII=31)
(ASCII=6
(ASCII=11)
(ASCII=15)
(ASCII=20)
....
you get the idea

In my case, the warning arose when convert.php descended into .git directories, which I would not expect to be handled correctly. @joelpittet can you confirm that you were running convert against a PHP file?

[joelpittet]

Oh I don't recall, it could have been going into the .git directory... They decided to build a PHPCodeSniffer rule for it instead.