Lock Travis distro so new future defaults will not break the build

clue · clue · commit 42e52ae7a43d · 2017-09-04T09:04:55.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -8,6 +8,9 @@ php:
   - 7.0
   - 7.1
 
+# lock distro so new future defaults will not break the build
+dist: precise
+
 # also test against HHVM, but require "trusty" and ignore errors
 matrix:
   include:
