Allow GHC 8.6.1 failures for now, it is still a pre-release.

svenpanne · svenpanne · commit d98c2d59bd4e · 2018-07-27T16:04:44.000+02:00
diff --git a/.travis.yml b/.travis.yml
@@ -63,6 +63,7 @@ matrix:
       addons: {apt: {packages: [ghc-ppa-tools,cabal-install-head,ghc-head], sources: [hvr-ghc]}}
 
   allow_failures:
+    - compiler: "ghc-8.6.1"
     - compiler: "ghc-head"
 
 before_install:
