misc/dump-stats.py: tool to show stats.json validity

Run like 'watch python misc/dump-stats.py' against a 'wormhole-server
start --stats-file=stats.json'

misc/dump-stats.py

@@ -0,0 +1,19 @@
+from __future__ import print_function
+import time, json
+
+# Run this as 'watch python misc/dump-stats.py' against a 'wormhole-server
+# start --stats-file=stats.json'
+
+with open("stats.json") as f:
+    data_s = f.read()
+
+now = time.time()
+data = json.loads(data_s)
+if now < data["valid_until"]:
+    valid = "valid"
+else:
+    valid = "EXPIRED"
+age = now - data["created"]
+
+print("age: %d (%s)" % (age, valid))
+print(data_s)