sslutil: set `_canloaddefaultcerts` to `True` if `ssl.SSLContext` is present The `load_default_certs()` method was already present when `ssl.SSLContext` was backported to Python 2.7 (https://hg.python.org/cpython/rev/221a1f9155e2).

#require docutils gettext

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