问google-api-client突然返回“无效请求”。

EN

def build_client(user_email)
  client = Google::APIClient.new
  client.authorization = Signet::OAuth2::Client.new(
  :token_credential_uri => 'https://accounts.google.com/o/oauth2/token',
  :audience => 'https://accounts.google.com/o/oauth2/token',
  :scope => 'https://www.googleapis.com/auth/calendar',
  :issuer => SERVICE_ACCOUNT_EMAIL,
  :signing_key => Google::APIClient::KeyUtils.load_from_pkcs12(SERVICE_ACCOUNT_PKCS12_FILE_PATH, "notasecret"),
   :person => user_email
  )
  client.authorization.fetch_access_token!    
  return client
end

Authorization failed.  Server message: (Signet::AuthorizationError)
{
  "error" : "invalid_request"
}