Special characters in the secret key cause failures

(This is not necessarily a bug in S3 CLI, but the bug does affect it.)

If the AWS secret key contains a special character (in my case, a `[`), the s3-cli commands do not work. Instead, the commands yield the error, `Error: The request signature we calculated does not match the signature you provided. Check your key and signing method.`

To work around the problem, issue yourself a new access key/secret key pair, where the latter does not have any special characters.