class Aws::Plugins::SignatureV4

def build_signer(cfg)
  if cfg.credentials && cfg.sigv4_region
    Aws::Sigv4::Signer.new(
      service: cfg.sigv4_name,
      region: cfg.sigv4_region,
      credentials_provider: cfg.credentials,
      unsigned_headers: ['content-length', 'user-agent', 'x-amzn-trace-id']
    )
  elsif cfg.credentials
    raise Errors::MissingRegionError
  elsif cfg.sigv4_region
    # Instead of raising now, we return a signer that raises only
    # if you attempt to sign a request. Some services have unsigned
    # operations and it okay to initialize clients for these services
    # without credentials. Unsigned operations have an "authtype"
    # trait of "none".
    MissingCredentialsSigner.new
  end
end