loadPasswordFromKeychain.swift

fileprivate func loadPasswordFromKeychainAndAuthenticateUser(_ account: String) {
  guard !account.isEmpty else { return }
  let passwordItem = KeychainPasswordItem(service:   KeychainConfiguration.serviceName, account: account, accessGroup: KeychainConfiguration.accessGroup)
  do {
      let storedPassword = try passwordItem.readPassword()
      authenticateUser(storedPassword)
  } catch KeychainPasswordItem.KeychainError.noPassword {
      print("No saved password")
  } catch {
      print("Unhandled error")
  }
}