class Aws::CredentialProviderChain

def env_credentials(options)
  env_keys = []
  if prefix = options[:prefix]
    env_keys << "#{prefix}_ACCESS_KEY_ID"
    env_keys << "#{prefix}_SECRET_ACCESS_KEY"
    env_keys << "#{prefix}_SESSION_TOKEN"
  else
    env_keys << options[:key]
    env_keys << options[:secret]
  end
  Credentials.new(*ENV.values_at(*env_keys))
end