結論から言うと オプション名が変更になっていた。
`proxy_uri` → `http_proxy`
参考: https://forums.aws.amazon.com/thread.jspa?threadID=172034
# 方法1
Aws.config[:access_key_id] = '(略)'
Aws.config[:secret_access_key] = '(略)'
Aws.config[:region] = 'ap-northeast-1'
Aws.config[:http_proxy] = 'http://user:password@your.proxy.example.com'
s3 = Aws::S3::Client.new
# 方法2
opt = {
access_key_id: '(略)',
secret_access_key: '(略)',
region: 'ap-northeast-1',
proxy_uri: 'http://user:password@your.proxy.example.com'
}
s3 = Aws::S3::Client.new(opt)