Update from 7x-1.7 to 7x-1.8 possibly broken

This issue presents itself as the following error:

$ drush @mysiteloc composer-manager update
You are running composer with xdebug enabled. This has a major impact on runtime performance. See https://getcomposer.org/xdebug
Loading composer repositories with package information
Updating dependencies (including require-dev)
Nothing to install or update
Generating autoload files
exception 'RuntimeException' with message 'Autoloader not found: ~/www/mysite/docroot/sites/all/libraries/composer/autoload.php' in              [error]
~/www/mysite/docroot/sites/all/modules/contrib/composer_manager/composer_manager.module:173
Stack trace:
#0 ~/www/mysite/docroot/sites/all/modules/contrib/composer_manager/composer_manager.drush.inc(162): composer_manager_register_autoloader()
#1 ~/www/mysite/docroot/sites/all/modules/contrib/composer_manager/composer_manager.drush.inc(101): drush_composer_manager_update_autoloader()
#2 [internal function]: drush_composer_manager('update')
#3 /usr/local/Cellar/drush/HEAD/libexec/includes/command.inc(359): call_user_func_array('drush_composer_...', Array)
#4 /usr/local/Cellar/drush/HEAD/libexec/includes/command.inc(210): _drush_invoke_hooks(Array, Array)
#5 [internal function]: drush_command('update')
#6 /usr/local/Cellar/drush/HEAD/libexec/includes/command.inc(178): call_user_func_array('drush_command', Array)
#7 /usr/local/Cellar/drush/HEAD/libexec/lib/Drush/Boot/BaseBoot.php(62): drush_dispatch(Array)
#8 /usr/local/Cellar/drush/HEAD/libexec/drush.php(70): Drush\Boot\BaseBoot->bootstrap_and_dispatch()
#9 /usr/local/Cellar/drush/HEAD/libexec/drush.php(11): drush_main()
#10 {main}
$

I've installed composer the following way:
drush @none dl composer-8

And I upgraded composer_manager from 7x-1.7 to 7x-1.8, and ran drush updatedb after.

I solved this by doing
drush dis composer_manager && drush pm-uninstall composer_manager

Had to disable/uninstall dependent modules.

But it fixed my problem.

I'm going to say that through this process I may have deleted the composer files in an attempt to re-install composer_manager's dependencies, so this may not be a module bug, but I wanted to file this bug in case others encounter this in the upgrade process.

Another idiosyncrasy of my install process was that I had previously installed Composer 7x and had to install 7x, so the install of composer_manager may have been broken by that.