Scripted updates fail between 8.7.0-beta1 and 8.7.3

[bobbygryzynger]

My system information:

• Operating system type: macOS
• Operating system version: 10.12.4
• BLT version: 8.7.0-beta1

When I run this command:

composer update acquia/blt --with-dependencies

I get the following output:

Updating BLT templated files...
Executing command (CWD): blt update
 > blt update
blt > blt:rsync-template:
     [echo] Copying files from BLT's template into your project...
blt > blt:update-yml:
     [echo] /Users/[user]/Sites/[site]/blt/project.yml was modified.
blt > blt:update-delta:
     [echo] Executing scripted updates for version 8006015
The following BLT updates are outstanding:
 - update_8007000: Updating composer.json to use wikimedia composer-merge-plugin.

Executing updates...
-> update_8007000: Updating composer.json to use wikimedia composer-merge-plugin.

Fatal error: Class 'Acquia\Blt\Robo\Common\ArrayManipulator' not found in /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updates.php on line 254

Call Stack:
    0.0002     234216   1. {main}() /Users/[user]/Sites/[site]/vendor/acquia/blt/bin/blt-console:0
    0.0169    2723672   2. Symfony\Component\Console\Application->run() /Users/[user]/Sites/[site]/vendor/acquia/blt/bin/blt-console:32
    0.0196    3088696   3. Symfony\Component\Console\Application->doRun() /Users/[user]/Sites/[site]/vendor/symfony/console/Application.php:122
    0.0197    3089776   4. Symfony\Component\Console\Application->doRunCommand() /Users/[user]/Sites/[site]/vendor/symfony/console/Application.php:191
    0.0198    3090424   5. Symfony\Component\Console\Command\Command->run() /Users/[user]/Sites/[site]/vendor/symfony/console/Application.php:846
    0.0202    3095808   6. Acquia\Blt\Console\Command\UpdateCommand->execute() /Users/[user]/Sites/[site]/vendor/symfony/console/Command/Command.php:267
    0.0354    3935224   7. Acquia\Blt\Update\Updater->executeUpdates() /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Console/Command/UpdateCommand.php:68
    0.0355    3936224   8. call_user_func:{/Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updater.php:165}() /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updater.php:165
    0.0355    3936800   9. Acquia\Blt\Update\Updates->update_8007000() /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updater.php:165

PHP Fatal error:  Class 'Acquia\Blt\Robo\Common\ArrayManipulator' not found in /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updates.php on line 254
PHP Stack trace:
PHP   1. {main}() /Users/[user]/Sites/[site]/vendor/acquia/blt/bin/blt-console:0
PHP   2. Symfony\Component\Console\Application->run() /Users/[user]/Sites/[site]/vendor/acquia/blt/bin/blt-console:32
PHP   3. Symfony\Component\Console\Application->doRun() /Users/[user]/Sites/[site]/vendor/symfony/console/Application.php:122
PHP   4. Symfony\Component\Console\Application->doRunCommand() /Users/[user]/Sites/[site]/vendor/symfony/console/Application.php:191
PHP   5. Symfony\Component\Console\Command\Command->run() /Users/[user]/Sites/[site]/vendor/symfony/console/Application.php:846
PHP   6. Acquia\Blt\Console\Command\UpdateCommand->execute() /Users/[user]/Sites/[site]/vendor/symfony/console/Command/Command.php:267
PHP   7. Acquia\Blt\Update\Updater->executeUpdates() /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Console/Command/UpdateCommand.php:68
PHP   8. call_user_func:{/Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updater.php:165}() /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updater.php:165
PHP   9. Acquia\Blt\Update\Updates->update_8007000() /Users/[user]/Sites/[site]/vendor/acquia/blt/src/Update/Updater.php:165

And I expected this to happen: the scripted updates to be performed without errors

[grasmash]

This has been addressed by #1551.