[Cache][Lock] Fix usages of error_get_last()

Author: nicolas-grekas

Store/FlockStore.php

@@ -78,8 +78,7 @@ private function lock(Key $key, $blocking)
         );
 
         // Silence error reporting
-        set_error_handler(function () {
-        });
+        set_error_handler(function ($type, $msg) use (&$error) { $error = $msg; });
         if (!$handle = fopen($fileName, 'r')) {
             if ($handle = fopen($fileName, 'x')) {
                 chmod($fileName, 0444);
@@ -91,8 +90,7 @@ private function lock(Key $key, $blocking)
         restore_error_handler();
 
         if (!$handle) {
-            $error = error_get_last();
-            throw new LockStorageException($error['message'], 0, null);
+            throw new LockStorageException($error, 0, null);
         }
 
         // On Windows, even if PHP doc says the contrary, LOCK_NB works, see