+ # expand_path translates '%%' into '%' and '$$' into '$'
+ # correspondingly that is not what we want since we need to keep
+ # '%%' intact for template dict substitution step. Working around
+ # with boundary-alike separator hack.
+ sep = ''.join([random.choice(ascii_letters) for _ in range(32)])
+ outtmpl = outtmpl.replace('%%', '%{0}%'.format(sep)).replace('$$', '${0}$'.format(sep))
+
+ # outtmpl should be expand_path'ed before template dict substitution
+ # because meta fields may contain env variables we don't want to
+ # be expanded. For example, for outtmpl "%(title)s.%(ext)s" and
+ # title "Hello $PATH", we don't want `$PATH` to be expanded.
+ filename = expand_path(outtmpl).replace(sep, '') % template_dict
+