Fatal error: Uncaught Error: Class 'Composer\Installers\BaseInstaller' not found in C:\SistemasPHP\observatorio4\vendor\composer\installers\src\Composer\Installers\MantisBTInstaller.php:6 Stack trace: #0 {main} thrown in C:\SistemasPHP\observatorio4\vendor\composer\installers\src\Composer\Installers\MantisBTInstaller.php on line 6