Pkgcore

- ebd: econf matches ``configure --help`` output better (ulm, 403)
- pytest.plugin.create_ebuild: insert blank line after ``EAPI=`` declare (arthurzam)

- domain: add support for ``-*`` and ``USE_EXPAND: -*`` syntax for packages.use like files (arthurzam, 393, 397)
- ebuild/test_eapi: fix tests artifacts in EBD_PATH (arthurzam, https://bugs.gentoo.org/888685)
- ebuild.repository: fix traversal from root of overlays (arthurzam, https://github.com/pkgcore/pkgcheck/issues/418)
- metadata.xsd: import ``kde-invent`` remote-ids (thesamesam , 399)
- various code cleanups, refactoring and modernization (arthurzam, ferringb)

- re-add Brian Harring (ferringb) as author for pkgcore
- properly close open file handlers during tests (arthurzam)
- various code cleanups, refactoring and modernization (ferringb)
- domain: fix parsing of multiple USE_EXAPNDs
(arthurzam, 391, https://bugs.gentoo.org/891409)
- portage_conf: add support for make.profile as its own directory, behaving as
specialized user profile (arthurzam, 390)

- _const: fallback to sys.base_prefix when installed in venv (arthurzam)
https://bugs.gentoo.org/880693
- pquery: fix crash with verbose single uris attr (arthurzam)
- docs: use snakeoil.dist sphinx extension (arthurzam)
- pkgcore: atom: fix typo in error message (thesamesam, 378)
- eclass: fix exported bash functions leak (arthurzam)
https://bugs.gentoo.org/836210
- remove plugins support from pkgcore, simplifying installation and stopping the need for users to update cache after upgrade (arthurzam, 379)
- add REQUIRED_USE satisfaction solver (arthurzam, 380)
- pmerge: add ``--pdb-intercept`` as a way to ``pdb.set_trace()`` into the resolver (ferringb)
- pmerge: sort target processing to stabilize the graph (ferringb)
- restricts: fix use default dep matching when working against IUSE defaults (ferringb)
- ebd: make EAPI=8 ``--disable-static`` logic libtool-specific, matching portage (SoapGentoo, 386)
- force stable sorting of ``/etc/portage/*`` files loading (ferringb)
https://github.com/pkgcore/pkgcore/issues/385
- add USE_EXPAND expansion awareness for ``/etc/portage/package.use/*`` files (ferringb)
https://github.com/pkgcore/pkgcore/issues/384
- add use flag validation for ``/etc/portage/package.use/*`` content (ferringb)
- throw an exception for any EBD var starting with ``_`` (ferringb)
- ignore both empty and non-existent ``repos.conf`` files (ferringb)
https://github.com/pkgcore/pkgcore/issues/365
- format code with ``black`` (ferringb, 382)
- various code cleanups, refactoring and modernization (ferringb)

- profiles: support package.bashrc files as an extension (370, arthurzam)
- patom: new command for working with atoms, like qatom (362, arthurzam)
- ebuild.repository: fix manifest entries generation with precise restricts (371, arthurzam)
- operations.fetch: better error messages when fetching fails (arthurzam)
https://github.com/pkgcore/pkgdev/issues/86
- ebuild.profiles: error out when USE_EXPAND syntax is used in package.mask (arthurzam)
https://github.com/pkgcore/pkgcheck/issues/370
- drop Python 3.8 support (arthurzam)
- Use flit with custom wrapper as build backend (372, 374, arthurzam, with special thanks to mgorny for reviewing and helping with it)

- portage_conf: fix timeout settings for rsync (368, arthurzam)
- fetch.custom: fix commands with `\` variable escaping (arthurzam)
https://github.com/pkgcore/pkgdev/issues/94
- repository: check issues with distdir only if fetch failed (arthurzam)
https://github.com/pkgcore/pkgdev/issues/99