py3: fix exception in pull when several things happen to a bookmark Specifically, when `changes` is: [(b'@upstream-committed', None, <function ui.status>, b'updating bookmark @upstream-committed\n'), (b'@upstream-committed', binary-node, <function ui.warn>, b'divergent bookmark @ stored as @upstream-committed\n')] sorting the list raises: TypeError: '<' not supported between instances of 'bytes' and 'NoneType' Differential Revision: https://phab.mercurial-scm.org/D8523