highlight: fix encoding issues to enable Py3 compatibility
This commit fixes various encoding issues with the `highlight` extension
to enable compatibility with Python 3. Python `.encode()` and `.decode()`
requires the target encoding to be passed as a `str`, so the value of
`mercurial.encoding.encoding` must be converted before passing to the
function. Pygments also assumes the `str` type for values it works with,
so we must perform conversions before and after receiving values from its
APIs.
After applying this patch, `test-highlight.t` passes under Python 3. We
add it to `python3-whitelist` as well.
Tested with Pygments 2.4.2.
Differential Revision: https://phab.mercurial-scm.org/D6832
== New Features ==
== New Experimental Features ==
== Bug Fixes ==
== Backwards Compatibility Changes ==
* A shell that supports `$(command)`` syntax for command substitution is now
required for running the test suite. The test runner normally uses
`sh`, so if that is a shell that doesn't support `$(command)` syntax,
you can override it by setting `$HGTEST_SHELL` or by passing it to
`run-tests.py --shell <shell>`.
== Internal API Changes ==