Saw these when looking at test results, https://dispatcher.drupalci.org/job/drupal_patches/66032/consoleFull
Perhaps related to #2877839: Reuse option in FileCopy migrate process plugin not work with remote files?
12:00:41 Notice: Constant FILE_EXISTS_RENAME already defined in /var/www/html/core/modules/migrate/tests/src/Unit/process/FileCopyTest.php on line 13
12:00:41
12:00:41 Notice: Constant FILE_EXISTS_REPLACE already defined in /var/www/html/core/modules/migrate/tests/src/Unit/process/FileCopyTest.php on line 18
12:00:41
12:00:41 Notice: Constant FILE_EXISTS_ERROR already defined in /var/www/html/core/modules/migrate/tests/src/Unit/process/FileCopyTest.php on line 23
12:00:41 PHP Notice: Constant FILE_EXISTS_RENAME already defined in /var/www/html/core/modules/migrate/tests/src/Unit/process/FileCopyTest.php on line 13
12:00:41 PHP Notice: Constant FILE_EXISTS_REPLACE already defined in /var/www/html/core/modules/migrate/tests/src/Unit/process/FileCopyTest.php on line 18
12:00:41 PHP Notice: Constant FILE_EXISTS_ERROR already defined in /var/www/html/core/modules/migrate/tests/src/Unit/process/FileCopyTest.php on line 23