server: add -n/--no-daemon, to run on py3

The twisted.python.logfile in Twisted-15.4.0 is not yet compatible with
py3, but can be bypassed by not daemonizing the server (so it doesn't
write to a logfile). This has been fixed in twisted trunk, so when
15.4.1 or 15.5.0 comes out, this will no longer be needed. But I think
we'll leave it in place, since sometimes it's handy to run a server
without daemonization.

src/wormhole/scripts/runner.py

@@ -40,6 +40,7 @@ sp_start.add_argument("--transit", default="tcp:3001", metavar="tcp:PORT",
                       help="endpoint specification for the transit-relay port")
 sp_start.add_argument("--advertise-version", metavar="VERSION",
                       help="version to recommend to clients")
+sp_start.add_argument("-n", "--no-daemon", action="store_true")
 #sp_start.add_argument("twistd_args", nargs="*", default=None,
 #                      metavar="[TWISTD-ARGS..]",
 #                      help=dedent("""\

src/wormhole/servers/cmd_server.py

@@ -22,8 +22,11 @@ def start_server(args):
 
     c = MyTwistdConfig()
     #twistd_args = tuple(args.twistd_args) + ("XYZ",)
-    twistd_args = ("XYZ",) # TODO: allow user to add twistd-specific args
-    c.parseOptions(twistd_args)
+    base_args = []
+    if args.no_daemon:
+        base_args.append("--nodaemon")
+    twistd_args = base_args + ["XYZ"]
+    c.parseOptions(tuple(twistd_args))
     c.loadedPlugins = {"XYZ": MyPlugin(args)}
 
     print("starting wormhole relay server")