Implement JSON validation in append.

poc/bin/kapow

@@ -279,7 +279,12 @@ def append_route(app):
     async def _append_route(request):
         """Create a new Kapow! route."""
         app.router._frozen = False
+
+        try:
             content = await request.json()
+        except Exception as exc:
+            return web.Response(status=400, reason="Malformed JSON")
+
         name = "ROUTE_" + str(uuid4()).replace('-', '_')
         try:
             app.router.add_route(content["method"],

spec/test/features/steps/steps.py

@@ -170,4 +170,7 @@ def step_impl(context):
 @when('I try to append with this malformed JSON document')
 @when('I try to append with this JSON document')
 def step_impl(context):
-    raise NotImplementedError('STEP: When I try to append with this JSON document')
+    context.response = requests.post(
+        f"{Env.KAPOW_CONTROLAPI_URL}/routes",
+        headers={"Content-Type": "application/json"},
+        data=context.text)