"CRITICAL Server: An error occurred during the Atlas print
WARNING: finish() called twice"

"if ( pkIndexes.size() < 1 )
    {
      throw QgsException( QStringLiteral( "An error occurred during the Atlas print" ) );
    }"

"QString errorString;
    atlas->setFilterExpression( filterString, errorString );
    if ( !errorString.isEmpty() )
    {
      throw QgsException( QStringLiteral( "An error occurred during the Atlas print" ) );
    }"