Update update_9001000 Fails

[mikemadison13]

When I run this command:

blt update

I get the following output:

-> update_9001000: Add deployment_identifier to project .gitignore and re-syncs ci.blt.yml.

 .gitignore has been updated. Review it for any custom changes that may have been overwritten. 


 blt/ci.blt.yml has been updated. Review it for any custom changes that may have been overwritten. 


Fatal error: Uncaught Error: Class 'Acquia\Blt\Update\ComposerMunge' not found in /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Update/Updates.php:567
Stack trace:
#0 [internal function]: Acquia\Blt\Update\Updates->update_9001000()
#1 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Update/Updater.php(171): call_user_func(Array)
#2 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Robo/Commands/Blt/UpdateCommand.php(291): Acquia\Blt\Update\Updater->executeUpdates(Array)
#3 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Robo/Commands/Blt/UpdateCommand.php(112): Acquia\Blt\Robo\Commands\Blt\UpdateCommand->executeSchemaUpdates('8009011')
#4 [internal function]: Acquia\Blt\Robo\Commands\Blt\UpdateCommand->update(Array)
#5 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/consolidation/annotated-command/src/CommandProcessor.php(235): call_user_func_array(Array, Array)
#6 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/consolidation/annotated-command/src/Comm in /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Update/Updates.php on line 567
PHP Fatal error:  Uncaught Error: Class 'Acquia\Blt\Update\ComposerMunge' not found in /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Update/Updates.php:567
Stack trace:
#0 [internal function]: Acquia\Blt\Update\Updates->update_9001000()
#1 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Update/Updater.php(171): call_user_func(Array)
#2 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Robo/Commands/Blt/UpdateCommand.php(291): Acquia\Blt\Update\Updater->executeUpdates(Array)
#3 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Robo/Commands/Blt/UpdateCommand.php(112): Acquia\Blt\Robo\Commands\Blt\UpdateCommand->executeSchemaUpdates('8009011')
#4 [internal function]: Acquia\Blt\Robo\Commands\Blt\UpdateCommand->update(Array)
#5 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/consolidation/annotated-command/src/CommandProcessor.php(235): call_user_func_array(Array, Array)
#6 /Users/mike.madison/git/Drupal-GovCon-2017/vendor/consolidation/annotated-command/src/Comm in /Users/mike.madison/git/Drupal-GovCon-2017/vendor/acquia/blt/src/Update/Updates.php on line 567
BLT update script failed! Run `blt blt:update --verbose` to retry.
You are using Drupal packages that are not supported by the Drupal Security Team!

And I expected this to happen:
the update runs