GrumPHP v0.14.x isn't compatible with Composer2.x

Author: leith

.travis.yml

@@ -39,7 +39,10 @@ matrix:
   allow_failures:	   
     - php: 5.6
     - php: 7.4
-    
+
+before_install:
+  - travis_retry composer self-update --1
+
 install:
   - if [[ $symfony != '*' ]]; then travis_retry composer require symfony/http-foundation:${symfony} --no-update --no-interaction; fi
   - if [[ $setup = 'basic' ]]; then travis_retry composer install --prefer-dist --no-interaction; fi