tests/test-gendoc-sv.t

histedit: binascii.unhexlify (aka node.bin) throws new exception type on py3

Lucky for us, the exception type exists on 2.7, so we can include it
in the except block without any extra work.

Differential Revision: https://phab.mercurial-scm.org/D2244

#require docutils gettext

  $ $TESTDIR/check-gendoc sv
  checking for parse errors