Adds a new exception to be able to distinguish that ClickHouse is not…

… available.

src/Exception/ClickHouseUnavailableException.php

@@ -0,0 +1,8 @@
+<?php
+
+declare(strict_types=1);
+
+namespace ClickHouseDB\Exception;
+
+final class ClickHouseUnavailableException extends QueryException {
+}

src/Statement.php

@@ -2,6 +2,7 @@
 
 namespace ClickHouseDB;
 
+use ClickHouseDB\Exception\ClickHouseUnavailableException;
 use ClickHouseDB\Exception\DatabaseException;
 use ClickHouseDB\Exception\QueryException;
 use ClickHouseDB\Query\Query;
@@ -176,6 +177,9 @@ public function error()
             $message = $this->response()->error();
         }
 
+        if ($code === CURLE_COULDNT_CONNECT) {
+            throw new ClickHouseUnavailableException($message, $code);
+        }
         throw new QueryException($message, $code);
     }