detect the error and throw before trying to execute, removing the 'Attempting to execute and unsuccesful or closed pending query result'

Author: Tishj

src/duckdb_py/pyconnection.cpp

@@ -465,6 +465,9 @@ shared_ptr<DuckDBPyConnection> DuckDBPyConnection::ExecuteMany(const py::object
 
 unique_ptr<QueryResult> DuckDBPyConnection::CompletePendingQuery(PendingQueryResult &pending_query) {
 	PendingExecutionResult execution_result;
+	if (pending_query.HasError()) {
+		pending_query.ThrowError();
+	}
 	while (!PendingQueryResult::IsResultReady(execution_result = pending_query.ExecuteTask())) {
 		{
 			py::gil_scoped_acquire gil;