update_payload: Fix most of lint styling issues.

This patch fixes a lot of pylint issues in the update_engine scripts. Majority
of this changes are based on recommendation found in:
	https://www.chromium.org/chromium-os/python-style-guidelines

It is a good idea to do these changes now, because if there are many pylint
errors when performing 'repo upload', serious problems can be overshadowed by a
lot of noise and eventually cause problems.

These fixes include:
	- Fixing executable shebangs to /usr/bin/python2.
	- Fixing import-error problems by disabiling them.
	- Removing pylint disables that are not valid anymore.
	- Changing all imports to proper absolute import format.
	- Change the import of PayloadError from update_payload.PayloadError for
	  simplicity.
	- Add pydoc strings for functions and classes that were missing.

The remaining unchanged pylint problmes include:

	- The header files of these scripts are in CrOS copyright format, but the
      the cros lint hook is configured to AoSP copyright format.
	- The test* functions in unittests are not compatible with CamelCase format.

BUG=chromium:796338
TEST=unittests pass
TEST=start_devserver
TEST=cros flash
TEST=scripts/paycheck.py

Change-Id: I7eed4d1625eb7c510c7949fada120de5a6a26c7b
Reviewed-on: https://chromium-review.googlesource.com/834875
Commit-Ready: Amin Hassani <ahassani@chromium.org>
Tested-by: Amin Hassani <ahassani@chromium.org>
Reviewed-by: Ben Chan <benchan@chromium.org>
Reviewed-by: Sen Jiang <senj@chromium.org>

1 files changed, 5 insertions, 3 deletions

diff --git a/scripts/blockdiff.py b/scripts/blockdiff.py
index feb5bd91..1dc60a68 100755
--- a/scripts/blockdiff.py
+++ b/scripts/blockdiff.py
@@ -1,4 +1,4 @@
-#!/usr/bin/python
+#!/usr/bin/python2
 #
 # Copyright (c) 2013 The Chromium OS Authors. All rights reserved.
 # Use of this source code is governed by a BSD-style license that can be
@@ -6,6 +6,8 @@
 
 """Block diff utility."""
 
+from __future__ import print_function
+
 import optparse
 import sys
 
@@ -92,7 +94,7 @@ def main(argv):
         diff_list = BlockDiff(opts.block_size, file1, file2, name1, name2,
                               opts.max_length)
   except BlockDiffError as e:
-    print >> sys.stderr, 'Error:', e
+    print('Error: ' % e, file=sys.stderr)
     return 2
 
   # Print the diff, if such was found.
@@ -103,7 +105,7 @@ def main(argv):
       print('%d->%d (%d)' %
             (extent_start, extent_start + extent_length, extent_length))
 
-    print 'total diff: %d blocks' % total_diff_blocks
+    print('total diff: %d blocks' % total_diff_blocks)
     return 1
 
   return 0