I have created a patch for migrate_spreadsheet, unfortunately it will not pass the testbot. Instead that gives me this (to me cryptic / uninformative) message:
fail: [run-tests.sh check] Line 0 of : FATAL Drupal\Tests\migrate_spreadsheet\Unit\SpreadsheetIteratorTest: test runner returned a non-zero error code (255).
Where/what is line 0? My first change compared to the original file was on line 7, where I corrected a class name. The only other two changes in that file where in the docs.
So what does this fail mean? How can I get more info from the testbot?