BaseTools: Refactor python except statements

Convert "except ... ," to "except ... as" to be compatible with python3.
Based on "futurize -f lib2to3.fixes.fix_except"

Contributed-under: TianoCore Contribution Agreement 1.1
Cc: Yonghong Zhu <yonghong.zhu@intel.com>
Cc: Liming Gao <liming.gao@intel.com>
Signed-off-by: Gary Lin <glin@suse.com>
Reviewed-by: Yonghong Zhu <yonghong.zhu@intel.com>

BaseTools/Source/Python/UPT/Library/CommentParsing.py

@@ -217,7 +217,7 @@ def ParsePcdErrorCode (Value = None, ContainerFile = None, LineNum = None):
         # To delete the tailing 'L'
         #
         return hex(ErrorCode)[:-1]
-    except ValueError, XStr:
+    except ValueError as XStr:
         if XStr:
             pass
         Logger.Error('Parser',