message: Also catch plain poplar_errors
diff: @@ -331,6 +331,8 @@ Status PoplarExceptionToTensorflowStatus(const std::string& prefix,
  return tensorflow::errors::ResourceExhausted(prefix, e.what());
  } catch (const poplar::index_error& e) {
  return tensorflow::errors::OutOfRange(prefix, e.what());
  + } catch (const poplar::poplar_error& e) {
  + return tensorflow::errors::Internal(prefix, e.what());
  }
  return tensorflow::errors::Unknown(prefix, e.what());
  