shelve: trust caller of shelvedfile.opener() to check that the file exists The only place we call `shelvedfile.opener()` is when we're about to apply a bundle. The file should always exist. If it doesn't, the `.hg/` directory is corrupt and we don't provide any guarantees about supporting corrupt repos (besides, telling the user that the shelve doesn't exist when `hg shelve --list` lists it is not very helpful). Differential Revision: https://phab.mercurial-scm.org/D9698

#require docutils gettext

  $ $TESTDIR/check-gendoc de
  checking for parse errors
  Die Dateien werden dem Projektarchiv beim n\xc3\xa4chsten \xc3\x9cbernehmen (commit) hinzugef\xc3\xbcgt. Um dies vorher r\xc3\xbcckg\xc3\xa4ngig zu machen, siehe:hg:`forget`. (esc)
  warning: please have a space before :hg: