tests/test-gendoc-ru.t

revlog: tweak wording and logic for flags validation

First, the logic around the if..elif..elif was subtly wrong
and sub-optimal because all branches would be tested as long as
the revlog was valid. This patch changes things so it behaves like
a switch statement over the revlog version.

While I was here, I also tweaked error strings to make them
consistent and to read better.

#require docutils gettext

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