Switch dkimsign.py to use dkim.DKIM directly rather than via dkim.dkim

Coerce argparse arguements to bytes so python3 works too

dkimsign.py

@@ -37,24 +37,38 @@ parser.add_argument('selector', action="store")
 parser.add_argument('domain', action="store")
 parser.add_argument('privatekeyfile', action="store")
 parser.add_argument('--hcanon', choices=['simple', 'relaxed'],
-    default='relaxed', type=bytes,
+    default='relaxed',
     help='Header canonicalization algorithm: default=relaxed')
 parser.add_argument('--bcanon', choices=['simple', 'relaxed'],
-    default='simple', type=bytes,
+    default='simple',
     help='Body canonicalization algorithm: default=simple')
 parser.add_argument('--identity', help='Optional value for i= tag.')
 args=parser.parse_args(arguments)
+signature_algorithm=b'rsa-sha256'
+include_headers = None
+length = None
+logger = None
 
 if sys.version_info[0] >= 3:
+    args.selector = bytes(args.selector, encoding='UTF-8')
+    args.domain = bytes(args.domain, encoding='UTF-8')
+    if args.identity is not None:
+        args.identity = bytes(args.identity, encoding='UTF-8')
+    args.hcanon = bytes(args.hcanon, encoding='UTF-8')
+    args.bcanon = bytes(args.bcanon, encoding='UTF-8')
     # Make sys.stdin and stdout binary streams.
     sys.stdin = sys.stdin.detach()
     sys.stdout = sys.stdout.detach()
+canonicalize = (args.hcanon, args.bcanon)
 
 message = sys.stdin.read()
 try:
-    sig = dkim.sign(message, args.selector, args.domain, open(
+    d = dkim.DKIM(message,logger=logger,
+                  signature_algorithm=signature_algorithm)
+    sig = d.sign(args.selector, args.domain, open(
                  args.privatekeyfile, "rb").read(), identity = args.identity,
-        canonicalize=(args.hcanon, args.bcanon))
+                 canonicalize=canonicalize, include_headers=include_headers,
+                 length=length)
     sys.stdout.write(sig)
     sys.stdout.write(message)
 except Exception as e: