changelog: prefilter in headrevs() In case where headrevs() is called on some revisions, we perform the check that aren't filtered in advance, and switch revlog to use its unchecked form. This allows to work with alternative implementations that don't have knowledge of the filtering system, such as the Rust one.

tests: fixed test too dependent on actual exception wording On one of the machines I use to run the tests prior to submission, the default Python is 2.7.5, with the following wording: must be encoded string without NULL bytes, not str This third form (and possible future ones) are motivation to use a wider catching regexp.