2.12.26: «The "composer.json" file includes the "require[magento/magento-composer-installer]" fields which have been deprecated and should not be present anymore.»: https://github.com/mage2pro/core/issues/34
2.12.26: «The "composer.json" file includes the "require[magento/magento-composer-installer]" fields which have been deprecated and should not be present anymore.»: https://github.com/mage2pro/core/issues/34

mage2pro/core,mage2pro/core,mage2pro/core