hack up vsctool to work with python 2 and 3

StringIO does not exist any more in python3, yet requiring 2.7 would
not pave the path forward, so try to be compatible with both.

Works for me on Python 2.7.9 and Python 3.4

I would appreciate if someone more fluent in serpentinous programming
language reviewed and/or rewrote this.

lib/libvcc/vsctool.py

@@ -37,7 +37,10 @@ import getopt
 import json
 import sys
 import gzip
-import StringIO
+try:
+    import StringIO
+except ImportError:
+    import io
 import collections
 import struct
 
@@ -54,9 +57,22 @@ PARAMS = {
 	"format":	[ "integer", FORMATS],
 }
 
+# http://python3porting.com/problems.html#bytes-strings-and-unicode
+if sys.version_info < (3,):
+    def b(x):
+        return x
+else:
+    import codecs
+    def b(x):
+        return codecs.latin_1_encode(x)[0]
+
 def gzip_str(s):
-	out = StringIO.StringIO()
-	gzip.GzipFile(fileobj=out, mode="w").write(s)
+	try:
+		out = StringIO.StringIO()
+	except NameError:
+		out = io.BytesIO()
+
+	gzip.GzipFile(fileobj=out, mode="w").write(b(s))
 	out.seek(4)
 	out.write(struct.pack("<L", 0x12bfd58))
 	return out.getvalue()
@@ -285,7 +301,7 @@ class rst_vsc(directive):
 	def __init__(self, s):
 		super(rst_vsc, self).__init__(s)
 
-		for i,v in PARAMS.iteritems():
+		for i,v in PARAMS.items():
 			if v is not True:
 				self.do_default(i, v[0], v[1])