Fix error code (#391)

* add failing test

* add fix

* eh adapt to older clickhouse too

Author: ruslandoga

lib/ch.ex

@@ -432,7 +432,7 @@ defmodule Ch do
       |> response_body_to_binary()
 
     code =
-      if code = get_header(headers, "x-clickhouse-error-code") do
+      if code = get_header(headers, "x-clickhouse-exception-code") do
         String.to_integer(code)
       end
 

test/ch/query_test.exs

@@ -468,11 +468,12 @@ defmodule Ch.QueryTest do
     end
 
     test "error code", %{conn: conn, query_options: query_options} do
-      assert {:error, %Ch.Error{code: code, message: message}} =
+      assert {:error,
+              %Ch.Error{
+                code: 62,
+                message: "Code: 62. DB::Exception: Syntax error: failed at position 1" <> _rest
+              }} =
                Ch.query(conn, "wat", [], query_options)
-
-      assert is_nil(code) or code == 62
-      assert message =~ "Code: 62"
     end
 
     test "connection works after failure in execute", %{conn: conn, query_options: query_options} do