Fix compatibility with python3 of clang-include-fixer.py

[yannack]

Summary

clang-include-fixer was recently updated to be python3-compatible.
However, an exception handling clause was improperly using the deprecated message property of Exception classes, so the code was not yet entirely python3-compatible.

[bkramer]

lg

clang-tools-extra/clang-include-fixer/tool/clang-include-fixer.py

if len(unique_headers) > 1:
           unique_headers, maximum_suggested_headers)
       inserted_header_infos = [
         header for header in header_infos if header["Header"] == selected]
     include_fixer_context["HeaderInfos"] = inserted_header_infos
 
     InsertHeaderToVimBuffer(include_fixer_context, text)
     print("Added #include {0} for {1}.".format(selected, symbol))
   except Exception as error:
-    print(error.message, file=sys.stderr)
+    print(error, file=sys.stderr)
   return
 
 
 if __name__ == '__main__':
   main()