windows: fix use of undefined exception (issue1707)
This fixes the implied reliance on pywin32 and the win32 module. This
also fixes a regression in ae275ad46bd0 that made Mercurial unusable
without pywin32.
changeset = '{rev}{tags}{parents} {node|short} {date|isodate} {author|user}\n {desc|firstline|strip}\n\n'
changeset_quiet = '{rev}:{node|short}\n'
changeset_verbose = '{rev}{tags}{parents} {node|short} {date|isodate} {author}\n {desc|strip}\n\n'
start_tags = '['
tag = '{tag},'
last_tag = '{tag}]'
start_parents = ':'
parent = '{rev},'
last_parent = '{rev}'