switch travis to bionic

This should solve the problem with pytest versions. Drop the notmuch
PPA, as (hopefully) we don't need those packages in bionic

diff --git a/.travis.yml b/.travis.yml
index 6c03f0fbb3e0dfdaf93b570a3d058ee7f5a66704..9dc03619560a0b10f9c058e3cd61ad307c3c9cdf 100644 (file)
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,12 +1,11 @@
 language: c
 
-dist: xenial
+dist: bionic
 
 addons:
   apt:
     sources:
     - sourceline: 'ppa:xapian-backports/ppa'
-    - sourceline: 'ppa:notmuch/notmuch'
     packages:
     - dtach
     - libxapian-dev