Setup error with Psr\\Log package

I have the same error on 3 different configurations

Code:

[Mon May 29 19:06:50.732166 2017] [php7:error] [pid 11572:tid 1292] [client 127.0.0.1:50241] PHP Fatal error:  
Interface 'Psr\\Log\\LoggerInterface' not found in C:\\**my_path**\\ci4app\\system\\Log\\Logger.php on line 55

I have a virtualhost but it probably does not matter ...

Code:

<VirtualHost ci4app:80>
 ServerName ci4app
# SetEnv CI_ENV development
  DocumentRoot "C:/**my_path**/ci4app/public"
<Directory "C:/**my_path**/ci4app/public">
Options Indexes FollowSymLinks
AllowOverride All
Require all granted
</Directory>
   ErrorLog "C:/**my_path**/ci4app/writable/logs/error.log"
   CustomLog "C:/**my_path**/ci4app/writable/logs/access.log" common
</VirtualHost>

You may need to set something in /Config/Logger.php