plugin: Add a test for timeout and broken manifest

Both of these plugins will fail in interesting ways, and we should
still handle them correctly.

Signed-off-by: Christian Decker <decker.christian@gmail.com>

contrib/plugins/fail/failtimeout.py

@@ -0,0 +1,58 @@
+#!/usr/bin/env python3
+"""An example plugin that fails to answer to `getmanifest`
+
+Used to test the `getmanifest` timeout.
+"""
+import json
+import sys
+import time
+
+
+def json_getmanifest(request):
+    # Timeout is 10 seconds, so wait 11
+    time.sleep(11)
+    return {
+        "options": [
+        ],
+        "rpcmethods": [
+        ]
+    }
+
+
+methods = {
+    'getmanifest': json_getmanifest,
+}
+
+
+partial = ""
+for l in sys.stdin:
+    try:
+        partial += l
+        request = json.loads(partial)
+    except Exception:
+        continue
+
+    result = None
+    method = methods[request['method']]
+    params = request['params']
+    try:
+        if isinstance(params, dict):
+            result = method(request, **params)
+        else:
+            result = method(request, *params)
+        result = {
+            "jsonrpc": "2.0",
+            "result": result,
+            "id": request['id']
+        }
+    except Exception as e:
+        result = {
+            "jsonrpc": "2.0",
+            "error": "Error while processing {}".format(request['method']),
+            "id": request['id']
+        }
+
+    json.dump(result, fp=sys.stdout)
+    sys.stdout.write('\n')
+    sys.stdout.flush()
+    partial = ""