electrum-ltc: unbreak (#368149)

Author: FliegendeWurst

pkgs/applications/misc/electrum/ltc.nix

@@ -109,6 +109,9 @@ python3.pkgs.buildPythonApplication {
     # copy the patched `/run_electrum` over `/electrum/electrum`
     # so the aiorpcx compatibility patch is used
     cp run_electrum electrum_ltc/electrum-ltc
+
+    # refresh stale generated code, per electrum_ltc/paymentrequest.py line 40
+    protoc --proto_path=electrum_ltc/ --python_out=electrum_ltc/ electrum_ltc/paymentrequest.proto
   '';
 
   preBuild =