chore(travis-ci): upgrade build environment to ubuntu bionic [skip appveyor]

lotem · lotem · commit 27ac4dd319a3 · 2019-12-18T01:47:13.000+08:00
diff --git a/.travis.yml b/.travis.yml
@@ -3,7 +3,7 @@ matrix:
   include:
   - os: linux
     compiler: gcc
-    dist: xenial
+    dist: bionic
     sudo: required
     install: "./travis-install.sh"
     script: make test
