[PATCH 1/1] BaseTools: explicitly import decode_header PatchCheck.py

["Leif Lindholm" <leif@nuviainc.com>]

On Debian 10 (Buster), when running PatchCheck.py with python2, a
backtrace is printed, starting from:

  File "../edk2/BaseTools/Scripts/PatchCheck.py", line 595, in find_patch_pieces
    parts = email.header.decode_header(pmail.get('subject'))
  AttributeError: 'module' object has no attribute 'header'

When using python3, this backtrace does not appear.

Explicitly importing decode_header resolves this for python2 and does not
appear to cause any issues with python3.

Cc: Bob Feng <bob.c.feng@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Leif Lindholm <leif@nuviainc.com>
---

I'm pretty sure this used to work with python 2,
but I'm not sure when it stopped...

 BaseTools/Scripts/PatchCheck.py | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/BaseTools/Scripts/PatchCheck.py b/BaseTools/Scripts/PatchCheck.py
index 13da6967785d..675ce273e830 100755
--- a/BaseTools/Scripts/PatchCheck.py
+++ b/BaseTools/Scripts/PatchCheck.py
@@ -19,6 +19,8 @@ import re
 import subprocess
 import sys
 
+from email.header import decode_header
+
 class Verbose:
     SILENT, ONELINE, NORMAL = range(3)
     level = NORMAL
-- 
2.20.1