tests: delete some no-py3 blocks And drop some nearby avoidable py3 checks in close proximity while we are here. Differential Revision: https://phab.mercurial-scm.org/D12257

tests: remove __future__ import from test-debugcommands.t This one is slightly more involved since it affects test output. Differential Revision: https://phab.mercurial-scm.org/D12256

tests: remove from __future__ from inline Python in tests This is no longer required since we require Python 3 and the linter no longer requires these statements. Differential Revision: https://phab.mercurial-scm.org/D12255

py2: remove simple from __future__ statements These were needed for Python 2 support. Now that our linter no longer mandates these, we can start deleting them. Differential Revision: https://phab.mercurial-scm.org/D12254

tests: remove output conditionalized on no-py3 I simply did a search for `^.* \(no-py3 !\)\n` and removed all matched lines. There are still some references to no-py3. But these were the simpler ones to match against. Differential Revision: https://phab.mercurial-scm.org/D12253

py3: use io.BytesIO directly Previously, pycompat.bytesio and pycompat.stringio referred to io.BytesIO. And util.bytesio and util.stringio aliased the pycompat symbols. This commit switches everything to use io.BytesIO directly. util.bytesio and util.stringio still exist to provide backwards compatibility, as they were the preferred symbols. Differential Revision: https://phab.mercurial-scm.org/D12252

check-py3-compat: drop support for Python 2 We no longer support Python 2 so we can drop support for linting code for Python 2 support. This gets rid of the check for `from __future__`, enabling us to delete those imports. Differential Revision: https://phab.mercurial-scm.org/D12251