pylightning: Fix the compat of `txprepare`

contrib/pylightning/lightning/lightning.py

@@ -891,7 +891,19 @@ class LightningRpc(UnixDomainSocketRpc):
 
         return self.call("withdraw", payload)
 
-    def txprepare(self, outputs, feerate=None, minconf=None, utxos=None):
+    def _deprecated_txprepare(self, destination, satoshi, feerate=None, minconf=None):
+        warnings.warn("txprepare now takes output arg: expect removal"
+                      " in Mid-2020",
+                      DeprecationWarning)
+        payload = {
+            "destination": destination,
+            "satoshi": satoshi,
+            "feerate": feerate,
+            "minconf": minconf,
+        }
+        return self.call("txprepare", payload)
+
+    def txprepare(self, *args, **kwargs):
         """
         Prepare a bitcoin transaction which sends to [outputs].
         The format of output is like [{address1: amount1},
@@ -901,6 +913,13 @@ class LightningRpc(UnixDomainSocketRpc):
         Outputs will be reserved until you call txdiscard or txsend, or
         lightningd restarts.
         """
+        if 'destination' in kwargs or 'satoshi' in kwargs:
+            return self._deprecated_txprepare(*args, **kwargs)
+
+        if not isinstance(args[0], list):
+            return self._deprecated_txprepare(*args, **kwargs)
+
+        def _txprepare(outputs, feerate=None, minconf=None, utxos=None):
             payload = {
                 "outputs": outputs,
                 "feerate": feerate,
@@ -909,6 +928,8 @@ class LightningRpc(UnixDomainSocketRpc):
             }
             return self.call("txprepare", payload)
 
+        return _txprepare(*args, **kwargs)
+
     def txdiscard(self, txid):
         """
         Cancel a bitcoin transaction returned from txprepare.  The outputs