code-php-fpm/Dockerfile STEP 15/30 fails: Could not find package drupal-composer/drupal-project with version 8.3.7

[kuilboer]

code-php-fpm/Dockerfile STEP 15/30:
RUN composer create-project drupal-composer/drupal-project:${DRUPAL_VERSION} /var/www/drupal/ --stability dev --no-interaction

The above statement references the drupal version, assuming the the version of the script: drupal-composer/drupal -project, is the same as the version of drupal to be installed. Acctually the the version for the script, as stated by drupal-project: refers to the actual version of the build script which seems to be unrelated to the version of Drupal.
In fact the Drupal version 8.3.7 cannot be references in the drupal-project context and triggers the version not found error.

replacing the variable ${DRUPAL_VERSION} for '8.x-dev' solves this issue.