`--environment` flag output appears to conflict with AWS CLI `credential_process` expected output

Hi there 👋 . Thanks for making this tool, it's great.

I might be off-base, but when I try to use the `--environment` flag in my `authenticate` command from `~/.aws/credentials`, I get the following error:

~/.aws/credentials
```
[my-profile]
credential_process = aws-okta-processor authenticate --organization *** --user *** --environment
```

```
$ aws s3 ls
...
Expecting value: line 1 column 1 (char 0)
```

This profile works fine:
~/.aws/credentials
```
[my-profile]
credential_process = aws-okta-processor authenticate --organization *** --user ***
```

I think that might be because credential_process expects JSON output on STDOUT?
https://docs.aws.amazon.com/cli/latest/userguide/cli-configure-sourcing-external.html
>>> The AWS CLI runs the command as specified in the profile and then reads data from STDOUT. The command you specify must generate JSON output on STDOUT that matches the following syntax.

Is that the case? Any workaround to get the `--environment` flag working when calling from an AWS named profile?