First observed on PR #823 and visible in the integration tests related to Requester Pays (build results)

Environment details

1. this library
2. OS type and version: N/A
3. Java version: N/A
4. version(s): all released prior to 2022-02-22

Code example

External references such as API reference guides

It seems the error message response changed subtly

- Bucket is requester pays bucket but no user project provided.
+ Bucket is a requester pays bucket but no user project provided.

According to public documentation, we should expect the reason to be userProjectMissing, however it is required as can be seen in

{
  "error": {
    "code": 400,
    "message": "Bucket is a requester pays bucket but no user project provided.",
    "errors": [
      {
        "message": "Bucket is a requester pays bucket but no user project provided.",
        "domain": "global",
        "reason": "required"
      }
    ]
  }
}

Related from NodeJS https://github.com/googleapis/nodejs-storage/pull/1791/files