templater: handle SyntaxError when parsing ui.logtemplate
Before, Mercurial would crash with a traceback ending with
SyntaxError: unmatched quotes
if you configured
[ui]
logtemplate = {rev}\n
The SyntaxError is now catched and the string is re-parsed without
requiring quotes.
ERROR: FIXME: This is a known failure of filelog.size for data starting with \1\n
OK.