improve error detection of OC API config file

oc_api/.httpkeys

+<?php
+
+$httpkeys = array(
+ 'OAuth2/client_id'    => 'e4XtMbKujytzMv9n',
+ 'OAuth2/basic_auth'   => 'e4XtMbKujytzMv9n:TJ9z2GaTBE33bChZRTMUgC3DwtcWt7xm',
+ 'OAuth2/redirect_uri' => 'https://pixees.fr/wp-content/plugins/class_code/oc_api',
+ 'OAuth2/log_email'    => 'thierry.vieville@inria.fr',
+ 'OAuth2/help_url'     => 'https://classcode.fr/accueil/aide?cc_mailer_shortcode_to=classcode-accueil%40inria.fr&cc_mailer_shortcode_who=Bureau%20d%C2%B4Accueil%20de%20Class%C2%B4Code&cc_mailer_shortcode_subject=Il%20y%20a%20un%20souci%20au%20nivau%20de%20la%20syndication%20avec%20OpenClassrooms#aideAction2',
+);
+
+?>

oc_api/OpenClassroomsAPI.php

@@ -439,6 +439,8 @@ class OpenClassroomsAPI {
       $httpkeys_file = plugin_dir_path( __FILE__ ).'.httpkeys';
       if (is_file($httpkeys_file)) {
 	include($httpkeys_file);
+	if (!(isset(self::$httpkeys) && isset(self::$httpkeys['client_id']) && isset(self::$httpkeys['basic_auth']) && isset(self::$httpkeys['reditect_url'])))
+	  self::reportLog("OpenClassroomsAPI::getAuth: Bad '.httpkeys' file format");
       } else {
 	self::reportLog("OpenClassroomsAPI::getAuth: Unable to read the '.httpkeys' file");
 	exit(0);