materio-base-d7/sites/all/modules/contrib/users/email_registration/email_registration.install

<?php

/**
 * @file
 * Checks requirements for the email_registration.module.
 */

/**
 * Implements hook_requirements().
 */
function email_registration_requirements() {
  $t = get_t();
  $requirements = array();

  if (module_exists('logintoboggan') && variable_get('logintoboggan_login_with_email', 0)) {
    $requirements['email_registration'] = array(
      'title' => $t('Email Registration / LoginToboggan Conflict'),
      'value' => $t('Conflict'),
      'description' => $t('There is a conflict between %email_registration and %logintoboggan. You should disable the "Allow users to login using their e-mail address" option from %logintoboggan.', array('%email_registration' => 'Email registration', '%logintoboggan' => 'Login Toboggan')),
      'severity' => REQUIREMENT_ERROR,
    );
  }

  return $requirements;
}