Check jinja templates for syntax error (kubernetes-sigs#10667)

Allow to fail early (pre-commit time) for jinja error, rather than
waiting until executing the playbook and the invalid template.

I could not find a simple jinja pre-commit hook in the wild.

.gitlab-ci/lint.yml

@@ -27,6 +27,14 @@ ansible-lint:
     - ansible-lint -v
   except: ['triggers', 'master']
 
+jinja-syntax-check:
+  extends: .job
+  stage: unit-tests
+  tags: [light]
+  script:
+    - "find -name '*.j2' -exec tests/scripts/check-templates.py {} +"
+  except: ['triggers', 'master']
+
 syntax-check:
   extends: .job
   stage: unit-tests

.pre-commit-config.yaml

@@ -69,3 +69,12 @@ repos:
         entry: tests/scripts/md-table/test.sh
         language: script
         pass_filenames: false
+
+      - id: jinja-syntax-check
+        name: jinja-syntax-check
+        entry: tests/scripts/check-templates.py
+        language: python
+        types:
+          - jinja
+        additional_dependencies:
+          - Jinja2

tests/scripts/check-templates.py

@@ -0,0 +1,9 @@
+#!/usr/bin/env python
+
+import sys
+from jinja2 import Environment
+
+env = Environment()
+for template in sys.argv[1:]:
+    with open(template) as t:
+        env.parse(t.read())