recurly-8.x-1.x-dev/modules/recurly_hosted/recurly_hosted.install

<?php

/**
 * @file
 * Install hooks for Recurly Hosted module.
 */

/**
 * Implements hook_requirements().
 */
function recurly_hosted_requirements($phase) {
  $requirements = [];
  if ($phase === 'install') {
    // Verify that recurlyjs isn't enabled at the same time.
    if (\Drupal::moduleHandler()->moduleExists('recurlyjs')) {
      $requirements['recurly_hosted_conflict'] = [
        'title' => t('Recurly.js conflict'),
        'description' => t('The "Recurly hosted pages" could not be enabled because the Recurly.js module is active. If specifically needing to use Recurly hosted pages, disable Recurly.js first.'),
        'severity' => REQUIREMENT_ERROR,
      ];
    }
  }
  return $requirements;
}