lib/spout changes break Excel export of tables

Prerequisite. Install https://github.com/mackensen/moodle-dataformat_markdown . Make sure you have debugging turned on. Test 1 Create a quiz with a 'True False' and a 'Short answer' question. Make two attempts at the quiz with different student accounts and make sure to submit and finish. Go to 'Quiz administration' -> 'Results' -> 'Statistics'. Download the entire report in different formats (except for Markdown as it is broken (in stable as well)). Take the downloaded files and open them in a text editor and confirm there are no PHP warnings/errors mixed up with the binary data. Confirm the files look good and are accurate when opened (for json confirm it is valid (eg. use https://jsonlint.com/ )). Test 2 Visit 'Site administration' > 'Users' > 'Bulk user actions'. Select a bunch of users then click on 'Add to selection'. In the select box 'With selected users...' select 'Download' and download a file for each format. Take the downloaded files and open them in a text editor and confirm there are no PHP warnings/errors mixed up with the binary data. Confirm the files look good and are accurate when opened (for json confirm it is valid (eg. use https://jsonlint.com/ )). For master only view your apache error log file and confirm there were messages warning abt the use of write_header() and write_footer() due to the markdown plugin. Test 3 Put the following code into a file called test.php and place it in your dirroot. <?php   require_once('config.php'); require_once($CFG->dirroot . '/mod/quiz/report/statistics/statistics_table.php');   $download = optional_param('download', '', PARAM_ALPHA);   $table = new quiz_statistics_table(); $table->is_downloading($download, 'test', get_string('quizstructureanalysis', 'quiz_statistics')); $exportclass = $table->export_class_instance(); $exportclass->start_table(get_string('quizinformation', 'quiz_statistics')); $exportclass->output_headers(array('Test heading 1', 'Test heading 2')); $exportclass->add_data(array('Test value 1', 'Test value 2')); $exportclass->finish_table(); $exportclass->finish_document(); Visit <yoursite>/test.php?download=<format> and confirm it works as expected. (Go through all the formats - csv, excel, html, json, markdown, ods - for json confirm it is valid (eg. use https://jsonlint.com/ )). For master only view your apache error log file and confirm there were messages warning abt the use of write_header() and write_footer() due to the markdown plugin.