Revert "Relax git_footers parsing to match that of Gerrit (JGit)."

This reverts commit 28a5d5defd13c382af94cd8368b16641752fee88.

Reason for revert: breaks assumption in function for adding footers

Original change's description:
> Relax git_footers parsing to match that of Gerrit (JGit).
> 
> R=​agable@chromium.org
> 
> Bug: 717504
> Change-Id: Ieb6415d55e85b91f11f9052b0fd08cf982b64d51
> Reviewed-on: https://chromium-review.googlesource.com/501849
> Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
> Reviewed-by: Aaron Gable <agable@chromium.org>
> 

TBR=agable@chromium.org,machenbach@chromium.org,tandrii@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
Bug: 717504

Change-Id: I9b4d619b2972be8434aff9464f1959fbcb3abd32
Reviewed-on: https://chromium-review.googlesource.com/503030
Reviewed-by: Andrii Shyshkalov <tandrii@chromium.org>
Commit-Queue: Andrii Shyshkalov <tandrii@chromium.org>
diff --git a/git_footers.py b/git_footers.py
index 31535c9..8e9aaff 100755
--- a/git_footers.py
+++ b/git_footers.py
@@ -48,8 +48,6 @@
   Guarantees that:
     (non_footer_lines + footer_lines) == message.splitlines().
     parsed_footers is parse_footer applied on each line of footer_lines.
-      There could be fewer parsed_footers than footer lines if some lines in
-      last paragraph are malformed.
   """
   message_lines = list(message.splitlines())
   footer_lines = []
@@ -63,8 +61,8 @@
     footer_lines = []
 
   footer_lines.reverse()
-  footers = filter(None, map(parse_footer, footer_lines))
-  if not footers:
+  footers = map(parse_footer, footer_lines)
+  if not footer_lines or not all(footers):
     return message_lines, [], []
   return message_lines[:-len(footer_lines)], footer_lines, footers