BaseTools/PatchCheck.py: Fix error when run with Python3

REF: https://bugzilla.tianocore.org/show_bug.cgi?id=1145

Currently run PatchCheck.py with Python3 will meet
following error:
.....
File "PatchCheck.py", line 554, in run_git
return Result[0].decode('utf-8', 'ignore') if Result[0] and
Result[0].find("fatal")!=0 else None
TypeError: a bytes-like object is required, not 'str'

This issue was introduce by commit:5ac4548cdf654.

This patch is to convert the str object of "fatal" to
byte object to fix this failure.

Cc: Liming Gao <liming.gao@intel.com>
Cc: Jaben Carsey <jaben.carsey@intel.com>
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Contributed-under: TianoCore Contribution Agreement 1.1
Signed-off-by: Dandan Bi <dandan.bi@intel.com>
Reviewed-by: Jaben Carsey <jaben.carsey@intel.com>
diff --git a/BaseTools/Scripts/PatchCheck.py b/BaseTools/Scripts/PatchCheck.py
index 96b3cdf..0b580f3 100755
--- a/BaseTools/Scripts/PatchCheck.py
+++ b/BaseTools/Scripts/PatchCheck.py
@@ -551,7 +551,7 @@
                      stdout=subprocess.PIPE,

                      stderr=subprocess.STDOUT)

         Result = p.communicate()

-        return Result[0].decode('utf-8', 'ignore') if Result[0] and Result[0].find("fatal")!=0 else None

+        return Result[0].decode('utf-8', 'ignore') if Result[0] and Result[0].find(b"fatal")!=0 else None

 

 class CheckOnePatchFile:

     """Performs a patch check for a single file.