py2: drop some more from __future__ statements These are no longer needed after dropping support for Python 2. Differential Revision: https://phab.mercurial-scm.org/D12258

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

pycompat: remove large Python 2 block We no longer support Python 2. So we can delete its compatibility code and remove the conditional and dedent the Python 3 code. In order to make the linter happy, we had to inline imports in the stanza at the top of the file. Differential Revision: https://phab.mercurial-scm.org/D12250

py3: use pickle directly pycompat.pickle abstracted over the different pickle modules in Python 2 and 3. Now that we're Python 3 only, it is safe to use the `pickle` module directly. So this commit does that. As part of this we remove the rules from check-code.py that were forbidden direct pickle module use. We retain the `util.pickle` symbol for backwards compatibility, just in case some extensions were using it. Differential Revision: https://phab.mercurial-scm.org/D12249

pycompat: remove first not ispy3 block We now require Python 3. So we can remove the first block supporting Python 2. Differential Revision: https://phab.mercurial-scm.org/D12247

import-checker: assume absolute and use modern import checker Since we require Python 3 now, we can assume we always use absolute imports and the modern import checker should be used. Differential Revision: https://phab.mercurial-scm.org/D12246

tests: unconditionalize some imports Now that we require Python 3 we can simplify these imports. Differential Revision: https://phab.mercurial-scm.org/D12245

tests: remove last references to PYTHON3 This removes the last references to PYTHON3. Differential Revision: https://phab.mercurial-scm.org/D12244

tests: simplify Windows and PYTHON3 conditionals PYTHON3 is always True. So this flow can be reduced. Differential Revision: https://phab.mercurial-scm.org/D12243

tests: delete some not PYTHON3 blocks These can never be used anymore. Differential Revision: https://phab.mercurial-scm.org/D12242

tests: unconditionalize _bytes2sys() As part of requiring Python 3. Differential Revision: https://phab.mercurial-scm.org/D12241

tests: remove Python 3 conditionalizing from variables Differential Revision: https://phab.mercurial-scm.org/D12240

tests: always encode session Differential Revision: https://phab.mercurial-scm.org/D12239

tests: unconditionalize bchr We could probably just do bytes([x]) everywhere. But this eliminates use of PYTHON3. Differential Revision: https://phab.mercurial-scm.org/D12238

tests: unconditionalize _unified_diff Now that we're Python 3 only we can make this logic simpler. Differential Revision: https://phab.mercurial-scm.org/D12237

tests: collapse elif PYTHON3 block PYTHON3 is always True now so this logic should be identical as to before. Differential Revision: https://phab.mercurial-scm.org/D12236

tests: collapse some more trivial if PYTHON3 blocks This doesn't account for all of the references to PYTHON3. But it accounts for the ones that are more trivial and don't entail logical changes. Differential Revision: https://phab.mercurial-scm.org/D12235

tests: require Python 3.5+ in run-tests.py We change the version check logic to hard fail if running on <= 3.5.0. The branch for <3.5 has been deleted. And the >=3.5 branch block has been dedented. Differential Revision: https://phab.mercurial-scm.org/D12234