NOTE: This was a time-sensitive article only valid before April 25, 2019; this is resolved as of Acquia Cloud 1.114.4 [ release notes ]
Before April 25. 2019, Acquia Cloud was experiencing a temporary issue involving drush aliases for all users of drush 9.3 or higher. A custom drush command (written for Acquia Hosting) utilizes code that became obsolete when drush factored SiteAlias classes out into the consolidation/site-alias project in drush 9.4. Drush extensions such as the ah-* drush commands that directly reference site alias classes must update namespaces in order for drush 9 to work as expected on Drupal 8.
This change currently prevents Drupal from being bootstrapped for all users of Drush 9 installed via composer with updated dependencies.
This issue appears in errors which resemble the following:
Fatal error: Declaration of Drush\Commands\AhSqlCommands::setSiteAliasManager($siteAliasManager) must be compatible with Consolidation\SiteAlias\SiteAliasManagerAwareInterface::setSiteAliasManager(Consolidation\SiteAlias\SiteAliasManagerInterface $siteAliasManager) in /etc/acquiadrush/commands/Commands/AhSqlCommands.php on line 8 [warning] Drush command terminated abnormally. Check for an exit() in your Drupal site.
ArgumentCountError: Too few arguments to function Drush\Sql\SqlBase::__construct(), 1 passed and exactly 2 expected in Drush\Sql\SqlBase->__construct() (line 34 of /mnt/www/html/[customer]/vendor/drush/drush/src/Sql/SqlBase.php). Drush command terminated abnormally due to an unrecoverable error.
Acquia is actively addressing this issue as urgent, and remediation will be announced as soon as possible.