InvalidArgumentException with message '$string ("") must be a string.'

I am trying to analyze a contributed module and upgrade it to D8. I keep getting exceptions though.

I downloaded the multicolumncheckboxesradios module (https://www.drupal.org/project/multicolumncheckboxesradios) into my modules directory, and ran "drush dmu-analyze multicolumncheckboxesradios"

Erichs-MacBook-Pro:wwwroot erich$ drush dmu-analyze multicolumncheckboxesradios
Indexing...done.
exception 'InvalidArgumentException' with message '$string ("") must be a string.' in                                                                [error]
/Users/erich/devel/sites/site/wwwroot/core/lib/Drupal/Core/StringTranslation/TranslatableMarkup.php:140
Stack trace:
#0 /Users/erich/devel/sites/site/wwwroot/core/lib/Drupal/Core/StringTranslation/StringTranslationTrait.php(71):
Drupal\Core\StringTranslation\TranslatableMarkup->__construct(NULL, Array, Array, Object(Drupal\Core\StringTranslation\TranslationManager))
#1 /Users/erich/devel/sites/site/wwwroot/modules/contrib/drupalmoduleupgrader/src/Plugin/DMU/Analyzer/FlagHookDeriver.php(47):
Drupal\drupalmoduleupgrader\DeriverBase->t(NULL, Array)
#2 /Users/erich/devel/sites/site/wwwroot/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php(100):
Drupal\drupalmoduleupgrader\Plugin\DMU\Analyzer\FlagHookDeriver->getDerivativeDefinitions(Array)
#3 /Users/erich/devel/sites/site/wwwroot/core/lib/Drupal/Component/Plugin/Discovery/DerivativeDiscoveryDecorator.php(86):
Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator->getDerivatives(Array)
#4 /Users/erich/devel/sites/site/wwwroot/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php(274):
Drupal\Component\Plugin\Discovery\DerivativeDiscoveryDecorator->getDefinitions()
#5 /Users/erich/devel/sites/site/wwwroot/core/lib/Drupal/Core/Plugin/DefaultPluginManager.php(174):
Drupal\Core\Plugin\DefaultPluginManager->findDefinitions()
#6 /Users/erich/devel/sites/site/wwwroot/modules/contrib/drupalmoduleupgrader/drupalmoduleupgrader.drush.inc(108):
Drupal\Core\Plugin\DefaultPluginManager->getDefinitions()
#7 /Users/erich/devel/sites/site/wwwroot/modules/contrib/drupalmoduleupgrader/drupalmoduleupgrader.drush.inc(244): _dmu_plugin_list('analyzer')
#8 [internal function]: drush_drupalmoduleupgrader_dmu_analyze('multicolumnchec...')
#9 phar:///usr/local/bin/drush/includes/command.inc(364): call_user_func_array('drush_drupalmod...', Array)
#10 phar:///usr/local/bin/drush/includes/command.inc(215): _drush_invoke_hooks(Array, Array)
#11 [internal function]: drush_command('multicolumnchec...')
#12 phar:///usr/local/bin/drush/includes/command.inc(183): call_user_func_array('drush_command', Array)
#13 phar:///usr/local/bin/drush/lib/Drush/Boot/BaseBoot.php(65): drush_dispatch(Array)
#14 phar:///usr/local/bin/drush/includes/preflight.inc(64): Drush\Boot\BaseBoot->bootstrap_and_dispatch()
#15 phar:///usr/local/bin/drush/includes/startup.inc(289): drush_main()
#16 phar:///usr/local/bin/drush/drush(114): drush_startup(Array)
#17 /usr/local/bin/drush(10): require('phar:///usr/loc...')
#18 {main}