D5684: py3: fix test-update-atomic.t

[durin42 (Augie Fackler)]

durin42 added inline comments.

INLINE COMMENTS

> pulkit wrote in test-update-atomic.t:13
> hm, why is this change required?

% python -c 'print(oct(10))'
  012
  % python3 -c 'print(oct(10))'
  0o12

REPOSITORY
  rHG Mercurial

REVISION DETAIL
  https://phab.mercurial-scm.org/D5684

To: durin42, pulkit, #hg-reviewers
Cc: mercurial-devel