bpo-36307: Travis: upgrade to Xenial environment (GH-12356)

methane · CAM-Gerlach · web-flow · commit 0f68d4af3b94 · 2019-03-19T18:08:36.000+09:00
(cherry picked from commit 74ae50e) Co-authored-by: CAM Gerlach <CAM.Gerlach@Gerlach.CAM>
diff --git a/.travis.yml b/.travis.yml
@@ -1,6 +1,5 @@
 language: c
-dist: trusty
-sudo: false
+dist: xenial
 group: beta
 
 # To cache doc-building dependencies and C compiler output.
