Deployment failures caused by config_split

[grasmash]

Deployments in acquia-pso/blted8 began failing after merge of #1102. See https://travis-ci.org/acquia-pso/blted8/builds/213255199.

exception 'UnexpectedValueException' with message                    [error]
'DirectoryIterator::__construct(../config/ci): failed to open dir: No
such file or directory' in
/home/travis/build/acquia-pso/blted8/docroot/core/lib/Drupal/Core/Config/FileStorage.php:316
Stack trace:
#0
/home/travis/build/acquia-pso/blted8/docroot/core/lib/Drupal/Core/Config/FileStorage.php(316):
DirectoryIterator->__construct('../config/ci')
#1
/home/travis/build/acquia-pso/blted8/docroot/core/lib/Drupal/Core/Config/FileStorage.php(282):
Drupal\Core\Config\FileStorage->getAllCollectionNamesHelper('../config/ci')
#2
/home/travis/build/acquia-pso/blted8/docroot/modules/contrib/config_split/src/Plugin/ConfigFilter/SplitFilter.php(290):
Drupal\Core\Config\FileStorage->getAllCollectionNames()
#3
/home/travis/build/acquia-pso/blted8/docroot/modules/contrib/config_filter/src/Config/FilteredStorage.php(217):
Drupal\config_split\Plugin\ConfigFilter\SplitFilter->filterGetAllCollectionNames(Array)
#4
/home/travis/build/acquia-pso/blted8/docroot/core/lib/Drupal/Core/Config/CachedStorage.php(247):
Drupal\config_filter\Config\FilteredStorage->getAllCollectionNames()
#5
/home/travis/build/acquia-pso/blted8/docroot/core/lib/Drupal/Core/Config/StorageComparer.php(455):
Drupal\Core\Config\CachedStorage->getAllCollectionNames()
#6
/home/travis/build/acquia-pso/blted8/docroot/core/lib/Drupal/Core/Config/StorageComparer.php(202):
Drupal\Core\Config\StorageComparer->getAllCollectionNames()
#7
/home/travis/build/acquia-pso/blted8/vendor/drush/drush/commands/core/config.drush.inc(682):
Drupal\Core\Config\StorageComparer->createChangelist()
#8 [internal function]: drush_config_import()
#9
/home/travis/build/acquia-pso/blted8/vendor/drush/drush/includes/command.inc(422):
call_user_func_array('drush_config_im...', Array)
#10
/home/travis/build/acquia-pso/blted8/vendor/drush/drush/includes/command.inc(231):
_drush_invoke_hooks(Array, Array)
#11 [internal function]: drush_command()
#12
/home/travis/build/acquia-pso/blted8/vendor/drush/drush/includes/command.inc(199):
call_user_func_array('drush_command', Array)
#13
/home/travis/build/acquia-pso/blted8/vendor/drush/drush/lib/Drush/Boot/BaseBoot.php(67):
drush_dispatch(Array)
#14
/home/travis/build/acquia-pso/blted8/vendor/drush/drush/includes/preflight.inc(66):
Drush\Boot\BaseBoot->bootstrap_and_dispatch()
#15
/home/travis/build/acquia-pso/blted8/vendor/drush/drush/drush.php(12):
drush_main()
#16 {main}
Command dispatch complete                                               [notice]
    [drush] Changing working directory back to /home/travis/build/acquia-pso/blted8/vendor/acquia/blt/phing.
[phingcall] /home/travis/build/acquia-pso/blted8/./vendor/acquia/blt/phing/tasks/setup.xml:271:8: /home/travis/build/acquia-pso/blted8/./vendor/acquia/blt/phing/tasks/setup.xml:283:36: Drush exited with code 1
[phingcall] /home/travis/build/acquia-pso/blted8/./vendor/acquia/blt/phing/tasks/setup.xml:255:22: Execution of the target buildfile failed. Aborting.
[phingcall] /home/travis/build/acquia-pso/blted8/./vendor/acquia/blt/phing/tasks/setup.xml:206:22: Execution of the target buildfile failed. Aborting.
BUILD FAILED/home/travis/build/acquia-pso/blted8/./vendor/acquia/blt/phing/tasks/ci.xml:14:22: Execution of the target buildfile failed. Aborting.
; 3 minutes  58.74 seconds

[grasmash]

Possibly caused by https://github.com/acquia/blt/blob/8.x/scripts/blt/ci/internal/config_split.config_split.ci.yml#L7, which is copied to https://github.com/acquia-pso/blted8/blob/8.x/config/default/config_split.config_split.ci.yml#L7.