revsets: make bookmark/named('re:nonexistent') not abort (issue6018) (BC) Foozy documented the differences between revsets branch(), tag(), bookmark(), and named() in eeb5d5ab14a6 (revset: raise RepoLookupError to make present() predicate continue the query, 2015-01-31). He seemed to want tag() to change behavior to not error out on non-matching regular expressions. I think it's instead bookmark() and named() that should not error out. So that's what this patch does. Differential Revision: https://phab.mercurial-scm.org/D5220