add stderr to scenario output

Author: m3dwards

src/warnet/server.py

@@ -165,10 +165,12 @@ def setup_rpc(self):
         self.jsonrpc.register(self.logs_grep)
 
     def scenario_log(self, proc):
-        while not proc.stdout:
+        while not proc.stdout and not proc.stderr:
             time.sleep(0.1)
         for line in proc.stdout:
             self.scenario_logger.info(line.decode().rstrip())
+        for line in proc.stderr:
+            self.scenario_logger.error(line.decode().rstrip())
 
     def get_warnet(self, network: str) -> Warnet:
         """