test: Remove nc.py

The nc.py script is only used in a single test, and for waiting for a
TCP port to be opened for listening.

This patch replaces it entirely, by using chamuyero for the test, and
bash for waiting on a TCP port.

test/util/lib.sh

@@ -61,10 +61,6 @@ function smtpc.py() {
 	${UTILDIR}/smtpc.py "$@"
 }
 
-function nc.py() {
-	${UTILDIR}/nc.py "$@"
-}
-
 function mail_diff() {
 	${UTILDIR}/mail_diff "$@"
 }
@@ -91,7 +87,7 @@ function fail() {
 function wait_until_ready() {
 	PORT=$1
 
-	while ! nc.py -z localhost $PORT; do
+	while ! bash -c "true < /dev/tcp/localhost/$PORT" 2>/dev/null ; do
 		sleep 0.1
 	done
 }

test/util/nc.py

@@ -1,50 +0,0 @@
-#!/usr/bin/env python3
-#
-# Simple "netcat" implementation.
-# Unfortunately netcat/nc is not that portable, so this contains a simple
-# implementation which fits our needs.
-
-import argparse
-import threading
-import smtplib
-import socket
-import sys
-
-ap = argparse.ArgumentParser()
-ap.add_argument("-z", action='store_true', help="scan for listening daemons")
-ap.add_argument("host", help="host to connect to")
-ap.add_argument("port", type=int, help="port to connect to")
-args = ap.parse_args()
-
-address = (args.host, args.port)
-
-try:
-	sock = socket.create_connection(address)
-	fd = sock.makefile('rw', buffering=1, encoding="utf-8")
-except OSError:
-	# Exit quietly, like nc does.
-	sys.exit(1)
-
-if args.z:
-	sys.exit(0)
-
-
-# stdin -> socket in the background. Do a partial shutdown when done.
-def stdin_to_sock():
-	for line in sys.stdin:
-		fd.write(line)
-		fd.flush()
-
-	try:
-		sock.shutdown(socket.SHUT_WR)
-	except OSError:
-		pass
-
-t1 = threading.Thread(target=stdin_to_sock, daemon=True)
-t1.start()
-
-# socket -> stdout in the foreground; if the socket closes, exit.
-for line in fd:
-	sys.stdout.write(line)
-	sys.stdout.flush()
-