Exposed a RESULT_DOWNLOAD_FILE_CANT_OPEN constant to docs and GDScript.

scene/main/http_request.cpp

@@ -480,8 +480,9 @@ void HTTPRequest::_bind_methods() {
 	BIND_CONSTANT( RESULT_NO_RESPONSE );
 	BIND_CONSTANT( RESULT_BODY_SIZE_LIMIT_EXCEEDED );
 	BIND_CONSTANT( RESULT_REQUEST_FAILED );
-	BIND_CONSTANT( RESULT_REDIRECT_LIMIT_REACHED );
+	BIND_CONSTANT( RESULT_DOWNLOAD_FILE_CANT_OPEN );
 	BIND_CONSTANT( RESULT_DOWNLOAD_FILE_WRITE_ERROR );
+	BIND_CONSTANT( RESULT_REDIRECT_LIMIT_REACHED );
 
 }