ci: Add pre-commit run and remove trailling spaces

.travis.yml

@@ -12,7 +12,27 @@ os: linux
 
 dist: xenial
 
+cache:
+  directories:
+  - "${HOME}/.cache/pip"
+  - "${HOME}/.cache/pre-commit"
+  - "${HOME}/.pre-commit-venv"
+  - "${HOME}/bin"
+  - /usr/lib/python3.8
+
 jobs:
+  include:
+  - language: go
+    go: "1.14"
+    name: Ubuntu 18.04
+    dist: bionic
+    sudo: required
+    before_script:
+      GO111MODULE=on go get mvdan.cc/sh/v3/cmd/shfmt;
+      curl https://pre-commit.com/install-local.py | python3 -
+    script:
+      SKIP=shellcheck pre-commit run --all-files;
+
   - <<: *native_job
     name: Ubuntu 16.04
 

test/lint-requirements.txt

@@ -0,0 +1 @@
+pre-commit==2.3.0