travis: uses xenial dist

dg · dg · commit cab6ac458baf · 2020-05-17T11:37:45.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -72,7 +72,9 @@ jobs:
         -   stage: Code Coverage
 
 
-sudo: false
+os: linux
+
+dist: xenial
 
 cache:
     directories:
