git-p4 tests: work with python3 as well as python2

Update the git-p4 tests so that they work with both
Python2 and Python3.

We have to be explicit about the difference between
Unicode text strings (Python3 default) and raw binary
strings which will be exchanged with Perforce.

Additionally, print always takes parentheses in Python3.

Signed-off-by: Luke Diamand <luke@diamand.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>

t/lib-git-p4.sh

@@ -198,9 +198,10 @@ marshal_dump() {
 	cat >"$TRASH_DIRECTORY/marshal-dump.py" <<-EOF &&
 	import marshal
 	import sys
+	instream = getattr(sys.stdin, 'buffer', sys.stdin)
 	for i in range($line):
-	    d = marshal.load(sys.stdin)
-	print d['$what']
+	    d = marshal.load(instream)
+	print(d[b'$what'].decode('utf-8'))
 	EOF
 	"$PYTHON_PATH" "$TRASH_DIRECTORY/marshal-dump.py"
 }

t/t9802-git-p4-filetype.sh

@@ -223,12 +223,12 @@ build_gendouble() {
 	import sys
 	import struct
 
-	s = struct.pack(">LL18s",
+	s = struct.pack(b">LL18s",
 			0x00051607,  # AppleDouble
 			0x00020000,  # version 2
-			""           # pad to 26 bytes
+			b""          # pad to 26 bytes
 	)
-	sys.stdout.write(s)
+	getattr(sys.stdout, 'buffer', sys.stdout).write(s)
 	EOF
 }