message: added ConnectionException as an OperationalError
diff: @@ -50,8 +50,9 @@ void RegisterExceptions(const py::module &m) {
  auto operational_error = py::register_exception<OperationalError>(m, "OperationalError", error).ptr();
  py::register_exception<TransactionException>(m, "TransactionException", operational_error);
  py::register_exception<OutOfMemoryException>(m, "OutOfMemoryException", operational_error);
  + py::register_exception<ConnectionException>(m, "ConnectionException", operational_error);
  // no object size error
  - // no null pointer error
  + // no null pointer errors
  py::register_exception<IOException>(m, "IOException", operational_error);
  py::register_exception<SerializationException>(m, "SerializationException", operational_error);
  