- Use newer version of shell pre-commit hooks.

- Use shellcheck from cabal instead from the Ubuntu package repo (which
has a newer version that supports --external-sources).

.pre-commit-config.yaml

@@ -6,7 +6,7 @@
     -   id: check-yaml
     -   id: check-merge-conflict
 -   repo: https://www.shore.co.il/git/shell-pre-commit/
-    sha: v0.5.3
+    sha: v0.5.4
     hooks:
     -   id: shell-lint
         files: shell-lint

.travis.yml

@@ -3,24 +3,30 @@ language: python
 python: "3.5"
 dist: trusty
 sudo: false
-
+group: beta
 cache:
   - pip
   - directories:
       - $HOME/.pre-commit
+      - $HOME/.cabal
+      - $HOME/.ghc
 
 addons:
   apt:
-    sources:
-      - sourceline: 'deb http://archive.ubuntu.com/ubuntu trusty-backports main universe multiverse'
     packages:
-      - shellcheck
+      - cabal-install
+      - ghc
+
+env:
+    PATH: $PATH:$HOME/.cabal/bin
 
 install:
-  - pip install pre_commit
+  - cabal update && cabal install shellcheck
+  - pip install pre_commit | cat
 
 script:
   - pre-commit run --all-files
 
 notifications:
+  on_failure: never
   email: false