Acquia Cloud Site Factory: Code deploy failures due to different Drupal versions

Issue

Unable to deploy new code because I'm receiving the following errors:

FATAL   [server-xxx] - Unable to proceed: could not retrieve Drupal version.

WARN    [server-xxxx] - Synchronous ssh - Verify if Drupal version is still the same inside "/mnt/tmp/repo_example/example_01test".

Resolution

From the docroot of both the existing code repository, as well as from the docroot of the new code repo to be deployed, run the following command to see if the Drupal version output matches:

$ drush8 status drupal-version

We expect there to be some sort of output from this command. The Drupal version output from both code repositories should match. If the new code does not match the existing code's Drupal version, the code deploy will fail and generate the above fatal error.

You will need to modify your code's Drupal version to match the existing Drupal version that is deployed in the current code repository.

Note: If you receive no output from running the drush status command, this indicates a code issue and not an Acquia Cloud Site Factory platform issue. 

Also, if the drush status command generates any output other than a Drupal version, this indicates a code issue, and further investigation into custom code by your development team will be needed.

Here are examples of other output generated by the drush status command, including no output:

$ drush8 status drupal-version
PHP Fatal error:  Class 'Symfony\Component\HttpFoundation\Request' not found in /Users/user/drush8/vendor/drush/drush/lib/Drush/Boot/DrupalBoot8.php on line 55

$ drush8 status drupal-version
user-1799:docroot user$

Cause

Code deployments in the Site Factory Management Console will fail when attempting to deploy a different major version of Drupal than expected.