Allow building with Python 3.x

Allow the scripts to run with both python 2.x and 3.x

Change-Id: I911118bcf370d09bdb2fb46afa21af64257f1ffb
Signed-off-by: Bernhard Rosenkränzer <Bernhard.Rosenkranzer@linaro.org>
diff --git a/mkbootimg/mkbootimg b/mkbootimg/mkbootimg
index aea2585..f95d703 100755
--- a/mkbootimg/mkbootimg
+++ b/mkbootimg/mkbootimg
@@ -19,6 +19,7 @@
 from os import fstat
 from struct import pack
 from hashlib import sha1
+import sys
 
 def filesize(f):
     if f is None:
@@ -133,8 +134,10 @@
     img_id = write_header(args)
     write_data(args)
     if args.id:
-        print('0x' + ''.join('{:02x}'.format(ord(c)) for c in img_id))
-
+        if isinstance(img_id, str):
+            # Python 2's struct.pack returns a string, but py3 returns bytes.
+            img_id = [ord(x) for x in img_id]
+        print('0x' + ''.join('{:02x}'.format(c) for c in img_id))
 
 if __name__ == '__main__':
     main()