tests/test_lightningd.py: add async option for pay command.

We'll need this for testing nodes going down during payment.

However, there's no good way to silence the threads that I can tell,
so we get a nasty backtrace from it.

Signed-off-by: Rusty Russell <rusty@rustcorp.com.au>

tests/test_lightningd.py

@@ -14,6 +14,7 @@ import sqlite3
 import string
 import sys
 import tempfile
+import threading
 import time
 import unittest
 import utils
@@ -195,21 +196,38 @@ class LightningDTests(BaseLightningDTests):
         l1.daemon.wait_for_log('-> CHANNELD_NORMAL')
         l2.daemon.wait_for_log('-> CHANNELD_NORMAL')
 
-    def pay(self, lsrc, ldst, amt, label=None):
+    def pay(self, lsrc, ldst, amt, label=None, async=False):
         if not label:
             label = ''.join(random.choice(string.ascii_letters + string.digits) for _ in range(20))
 
         rhash = ldst.rpc.invoice(amt, label)['rhash']
         assert ldst.rpc.listinvoice(label)[0]['complete'] == False
 
-        routestep = {
-            'msatoshi' : amt,
-            'id' : ldst.info['id'],
-            'delay' : 5,
-            'channel': '1:1:1'
-        }
-        lsrc.rpc.sendpay(to_json([routestep]), rhash)
-        assert ldst.rpc.listinvoice(label)[0]['complete'] == True
+        def call_pay():
+            routestep = {
+                'msatoshi' : amt,
+                'id' : ldst.info['id'],
+                'delay' : 5,
+                'channel': '1:1:1'
+            }
+            lsrc.rpc.sendpay(to_json([routestep]), rhash, async=False)
+
+        t = threading.Thread(target=call_pay)
+        t.daemon = True
+        t.start()
+
+        def wait_pay():
+            # Up to 10 seconds for payment to succeed.
+            start_time = time.time()
+            while not ldst.rpc.listinvoice(label)[0]['complete']:
+                if time.time() > start_time + 10:
+                    raise TimeoutError('Payment timed out')
+                time.sleep(0.1)
+
+        if async:
+            return self.executor.submit(wait_pay)
+        else:
+            return wait_pay()
 
     def test_connect(self):
         l1,l2 = self.connect()