vim: Make format plugin work with py2 and py3

Google's Linux distro's Vim seems to have dropped +python, so port the
format script to work with both 2 and 3.

Change-Id: I4d6b3876cf159791f16cd8109c31b4219ddc8983
Reviewed-on: https://gn-review.googlesource.com/c/gn/+/7240
Commit-Queue: Nico Weber <thakis@chromium.org>
Reviewed-by: Nico Weber <thakis@chromium.org>

misc/vim/gn-format.py

diff --git a/misc/vim/gn-format.py b/misc/vim/gn-format.py
index 6170851..f21f1b9 100644
--- a/misc/vim/gn-format.py
+++ b/misc/vim/gn-format.py
@@ -18,6 +18,7 @@
 import subprocess
 import sys
 import vim
+from __future__ import print_function
 
 # Change this to the full path if gn is not on the path.
 binary = 'gn'
@@ -44,8 +45,8 @@
                        shell=is_win, universal_newlines=True)
   stdout, stderr = p.communicate(input=text)
   if p.returncode != 0:
-    print 'Formatting failed, please report to gn-dev@chromium.org.'
-    print stdout, stderr
+    print('Formatting failed, please report to gn-dev@chromium.org.')
+    print(stdout, stderr)
   else:
     # Otherwise, replace current buffer.
     lines = stdout.split('\n')