Add Symfony 6 support

Author: sylvaindeloux

composer.json

@@ -14,14 +14,14 @@
     "require": {
         "php": ">=5.5",
         "aws/aws-sdk-php": "^3.2.6",
-        "symfony/config": "~2.3|~3.0|~4.0|~5.0",
-        "symfony/dependency-injection": "~2.3|~3.0|~4.0|~5.0",
-        "symfony/http-kernel": "~2.3|~3.0|~4.0|~5.0"
+        "symfony/config": "~2.3|~3.0|~4.0|~5.0|~6.0",
+        "symfony/dependency-injection": "~2.3|~3.0|~4.0|~5.0|~6.0",
+        "symfony/http-kernel": "~2.3|~3.0|~4.0|~5.0|~6.0"
     },
     "require-dev": {
         "phpunit/phpunit": "^4.8.35|^5.4.0|^6.0.0",
-        "symfony/framework-bundle": "~2.3|~3.0|~4.0|~5.0",
-        "symfony/yaml": "~2.3|~3.0|~4.0|~5.0"
+        "symfony/framework-bundle": "~2.3|~3.0|~4.0|~5.0|~6.0",
+        "symfony/yaml": "~2.3|~3.0|~4.0|~5.0|~6.0"
     },
     "autoload": {
         "psr-4": {