update_payload: Port scripts to python3

Update the update_payload scripts to be compatible with
python2 and python3. Python2 compatibility is needed since
the repo is shared with Android.

BUG=chromium:1011631

TEST=Executed aosp/system/update_engine/scripts/run_unittests and
cros_generate_update_payload

Cq-Depend: chromium:1904837, chromium:1911499
Change-Id: Ie450b80b5f7550051b38d320173ccc0c915f65e7
Reviewed-on: https://chromium-review.googlesource.com/c/aosp/platform/system/update_engine/+/1904310
Commit-Queue: Andrew Lassalle <andrewlassalle@chromium.org>
Tested-by: Andrew Lassalle <andrewlassalle@chromium.org>
Reviewed-by: Mike Frysinger <vapier@chromium.org>
Reviewed-by: Amin Hassani <ahassani@chromium.org>
Auto-Submit: Andrew Lassalle <andrewlassalle@chromium.org>
diff --git a/scripts/update_payload/applier.py b/scripts/update_payload/applier.py
index 511ed49..7830c00 100644
--- a/scripts/update_payload/applier.py
+++ b/scripts/update_payload/applier.py
@@ -24,6 +24,7 @@
 
 """
 
+from __future__ import absolute_import
 from __future__ import print_function
 
 import array
@@ -70,7 +71,7 @@
   """
   hasher = hashlib.sha256()
   block_length = 1024 * 1024
-  max_length = length if length >= 0 else sys.maxint
+  max_length = length if length >= 0 else sys.maxsize
 
   while max_length > 0:
     read_length = min(max_length, block_length)
@@ -108,7 +109,7 @@
   """
   data = array.array('c')
   if max_length < 0:
-    max_length = sys.maxint
+    max_length = sys.maxsize
   for ex in extents:
     if max_length == 0:
       break
@@ -176,7 +177,7 @@
   arg = ''
   pad_off = pad_len = 0
   if data_length < 0:
-    data_length = sys.maxint
+    data_length = sys.maxsize
   for ex, ex_name in common.ExtentIter(extents, base_name):
     if not data_length:
       raise PayloadError('%s: more extents than total data length' % ex_name)
@@ -416,7 +417,7 @@
                          "--dst_extents=%s" % out_extents_arg]
         subprocess.check_call(puffpatch_cmd)
       else:
-        raise PayloadError("Unknown operation %s", op.type)
+        raise PayloadError("Unknown operation %s" % op.type)
 
       # Pad with zeros past the total output length.
       if pad_len:
@@ -451,7 +452,7 @@
                          "--patch_file=%s" % patch_file_name]
         subprocess.check_call(puffpatch_cmd)
       else:
-        raise PayloadError("Unknown operation %s", op.type)
+        raise PayloadError("Unknown operation %s" % op.type)
 
       # Read output.
       with open(out_file_name, 'rb') as out_file: