paycheck: strip newlines off of hash digest strings

This is an annoyance I'd like to get rid of.

BUG=None
TEST=None

Change-Id: I6119163ffc4944dd2f857bad055822b37229a692
Reviewed-on: https://chromium-review.googlesource.com/176478
Tested-by: Gilad Arnold <garnold@chromium.org>
Reviewed-by: Don Garrett <dgarrett@chromium.org>
Commit-Queue: Gilad Arnold <garnold@chromium.org>

scripts/update_payload/common.py

diff --git a/scripts/update_payload/common.py b/scripts/update_payload/common.py
index a869730..584eb35 100644
--- a/scripts/update_payload/common.py
+++ b/scripts/update_payload/common.py
@@ -132,7 +132,7 @@
 
 def FormatSha256(digest):
   """Returns a canonical string representation of a SHA256 digest."""
-  return digest.encode('base64')
+  return digest.encode('base64').strip()
 
 
 #