minor #582 add php 7.4 (andreybolonin)

This PR was merged into the 1.5-dev branch.

Discussion
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add php 7.4

Commits
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e09c7e6 add php 7.4

Author: nicolas-grekas

.travis.yml

@@ -9,6 +9,7 @@ matrix:
       env: COMPOSER_FLAGS='--prefer-lowest'
     - php: 7.2
     - php: 7.3
+    - php: 7.4
   fast_finish: true
 
 cache:

phpunit.xml.dist

@@ -18,6 +18,7 @@
 
   <php>
     <ini name="error_reporting" value="-1" />
+    <env name="SYMFONY_DEPRECATIONS_HELPER" value="weak" />
   </php>
 
   <filter>