Enforce that changelog files are .rst

.pre-commit-config.yaml

@@ -38,3 +38,8 @@ repos:
         language: python
         additional_dependencies: [pygments, restructuredtext_lint]
         python_version: python3.6
+    -   id: changelogs-rst
+        name: changelog files must end in .rst
+        entry: ./scripts/fail
+        language: script
+        files: 'changelog/.*(?<!\.rst)$'

scripts/fail

@@ -0,0 +1,7 @@
+#!/usr/bin/env python
+"""Used by .pre-commit-config.yaml"""
+import sys
+
+if __name__ == "__main__":
+    print(" ".join(sys.argv[1:]))
+    sys.exit(1)