Avoid using non-ASCII characters in exception messages
So, we bumped into the famous
```
"Missing multipart field \u2018operations\u2019 (https://github.com/jaydenseric/graphql-multipart-request-spec)."
```
The reverse apostrophe and the mirrored apostrophe do not look well in my server logs terminal.

Best practice for backend engineering:
* use ASCII only characters in log messages,
* this means to use ASCII only characters in error (exception) messages.

Should I submit a PR to use `'` or `"` or else instead of the `\u2018` and `\u2019`?