Issue #1333940 by yesct, quietone, pingers, chx, catch: Try to use is_file()...

Issue #1333940 by yesct, quietone, pingers, chx, catch: Try to use is_file() instead of file_exists() in DrupalKernel::findSitePath()

core/lib/Drupal/Core/DrupalKernel.php

@@ -404,7 +404,7 @@ public static function findSitePath(Request $request, $require_settings = TRUE,
 
     // Determine whether multi-site functionality is enabled. If not, return
     // the default directory.
-    if (!file_exists($app_root . '/sites/sites.php')) {
+    if (!is_file($app_root . '/sites/sites.php')) {
       return 'sites/default';
     }
 
@@ -435,10 +435,10 @@ public static function findSitePath(Request $request, $require_settings = TRUE,
         // If the identifier is a key in $sites, check for a directory matching
         // the corresponding value. Otherwise, check for a directory matching
         // the identifier.
-        if (isset($sites[$site_id]) && file_exists($app_root . '/sites/' . $sites[$site_id])) {
+        if (isset($sites[$site_id]) && is_dir($app_root . '/sites/' . $sites[$site_id])) {
           $site_id = $sites[$site_id];
         }
-        if (file_exists($app_root . '/sites/' . $site_id . '/settings.php') || (!$require_settings && file_exists($app_root . '/sites/' . $site_id))) {
+        if (is_file($app_root . '/sites/' . $site_id . '/settings.php') || (!$require_settings && is_file($app_root . '/sites/' . $site_id))) {
           return "sites/$site_id";
         }
       }
@@ -649,7 +649,7 @@ public function discoverServiceProviders() {
         $this->serviceProviderClasses['app'][$module] = $class;
       }
       $filename = dirname($filename) . "/$module.services.yml";
-      if (file_exists($filename)) {
+      if (is_file($filename)) {
         $this->serviceYamls['app'][$module] = $filename;
       }
     }
@@ -1663,7 +1663,7 @@ protected static function setupTrustedHosts(Request $request, $host_patterns) {
    *   A list of service files.
    */
   protected function addServiceFiles(array $service_yamls) {
-    $this->serviceYamls['site'] = array_filter($service_yamls, 'file_exists');
+    $this->serviceYamls['site'] = array_filter($service_yamls, 'is_file');
   }
 
   /**