Fix deprecations helper crashing old Symfony versions

Author: curry684

.travis.yml

@@ -18,13 +18,21 @@ matrix:
     fast_finish: true
     include:
      - php: 7.2
-       env: SYMFONY_VERSION=4.1
+       env:
+         - SYMFONY_VERSION=4.1.13
+         - SYMFONY_DEPRECATIONS_HELPER=weak
      - php: 7.2
-       env: COMPOSER_FLAGS="--prefer-lowest"
+       env:
+         - COMPOSER_FLAGS="--prefer-lowest"
+         - SYMFONY_DEPRECATIONS_HELPER=weak
      - php: 7.3
-       env: SYMFONY_VERSION=^4.4
+       env:
+         - SYMFONY_VERSION=^4.4
+         - SYMFONY_DEPRECATIONS_HELPER=weak
      - php: 7.4
-       env: SYMFONY_VERSION=^4.4
+       env:
+         - SYMFONY_VERSION=^4.4
+         - SYMFONY_DEPRECATIONS_HELPER=weak
      - php: 7.4
        env: DEPENDENCIES=dev
      - php: nightly

tests/Fixtures/config.yml

@@ -42,6 +42,7 @@ doctrine:
 twig:
     debug: '%kernel.debug%'
     strict_variables: '%kernel.debug%'
+    exception_controller: null
 
 datatables:
     options: