Added an error code to some error messages

src/p2p_server.cpp

@@ -438,7 +438,7 @@ void P2PServer::save_peer_list()
 	std::ofstream f(saved_peer_list_file_name, std::ios::binary);
 
 	if (!f.is_open()) {
-		LOGERR(1, "failed to save peer list");
+		LOGERR(1, "failed to save peer list " << saved_peer_list_file_name << ", error " << errno);
 		return;
 	}
 

src/p2pool.cpp

@@ -1695,6 +1695,9 @@ void p2pool::api_update_block_found(const ChainMain* data, const PoolBlock* bloc
 			f.flush();
 			f.close();
 		}
+		else {
+			LOGERR(1, "Failed to update " << FOUND_BLOCKS_FILE << ", error " << errno);
+		}
 	}
 
 	std::vector<FoundBlock> found_blocks;