Remove MANIFEST.in and related lint check

[nicoddemus]

Because setuptools_scm already includes all version-controlled files
in an sdist, we don't need to maintain a MANIFEST.in file and anymore

See pytest-dev/pytest-xdist#161

Here's the contents of the SOURCES.txt file after running pytest setup.py sdist:

.coveragerc
.gitattributes
.gitignore
.travis.yml
AUTHORS
CHANGELOG.rst
CONTRIBUTING.rst
HOWTORELEASE.rst
LICENSE
README.rst
appveyor.yml
pyproject.toml
pytest.py
setup.cfg
setup.py
tox.ini
.github/ISSUE_TEMPLATE.md
.github/PULL_REQUEST_TEMPLATE.md
_pytest/__init__.py
_pytest/_argcomplete.py
_pytest/_pluggy.py
_pytest/_version.py
_pytest/cacheprovider.py
_pytest/capture.py
_pytest/compat.py
_pytest/config.py
_pytest/debugging.py
_pytest/deprecated.py
_pytest/doctest.py
_pytest/fixtures.py
_pytest/freeze_support.py
_pytest/helpconfig.py
_pytest/hookspec.py
_pytest/impl
_pytest/junitxml.py
_pytest/main.py
_pytest/mark.py
_pytest/monkeypatch.py
_pytest/nose.py
_pytest/pastebin.py
_pytest/pytester.py
_pytest/python.py
_pytest/recwarn.py
_pytest/resultlog.py
_pytest/runner.py
_pytest/setuponly.py
_pytest/setupplan.py
_pytest/skipping.py
_pytest/terminal.py
_pytest/tmpdir.py
_pytest/unittest.py
_pytest/warnings.py
_pytest/_code/__init__.py
_pytest/_code/_py2traceback.py
_pytest/_code/code.py
_pytest/_code/source.py
_pytest/assertion/__init__.py
_pytest/assertion/rewrite.py
_pytest/assertion/truncate.py
_pytest/assertion/util.py
_pytest/vendored_packages/README.md
_pytest/vendored_packages/__init__.py
_pytest/vendored_packages/pluggy.py
_pytest/vendored_packages/pluggy-0.4.0.dist-info/DESCRIPTION.rst
_pytest/vendored_packages/pluggy-0.4.0.dist-info/INSTALLER
_pytest/vendored_packages/pluggy-0.4.0.dist-info/LICENSE.txt
_pytest/vendored_packages/pluggy-0.4.0.dist-info/METADATA
_pytest/vendored_packages/pluggy-0.4.0.dist-info/RECORD
_pytest/vendored_packages/pluggy-0.4.0.dist-info/WHEEL
_pytest/vendored_packages/pluggy-0.4.0.dist-info/metadata.json
_pytest/vendored_packages/pluggy-0.4.0.dist-info/top_level.txt
bench/bench.py
bench/bench_argcomplete.py
bench/empty.py
bench/manyparam.py
bench/skip.py
changelog/2434.bugfix
changelog/2440.bugfix
changelog/2464.bugfix
changelog/2493.doc
changelog/2499.trivial
changelog/_template.rst
doc/en/Makefile
doc/en/adopt.rst
doc/en/assert.rst
doc/en/backwards-compatibility.rst
doc/en/bash-completion.rst
doc/en/builtin.rst
doc/en/cache.rst
doc/en/capture.rst
doc/en/changelog.rst
doc/en/check_sphinx.py
doc/en/conf.py
doc/en/conftest.py
doc/en/contact.rst
doc/en/contents.rst
doc/en/contributing.rst
doc/en/customize.rst
doc/en/doctest.rst
doc/en/existingtestsuite.rst
doc/en/faq.rst
doc/en/fixture.rst
doc/en/funcarg_compare.rst
doc/en/funcargs.rst
doc/en/genapi.py
doc/en/getting-started.rst
doc/en/goodpractices.rst
doc/en/index.rst
doc/en/license.rst
doc/en/links.inc
doc/en/mark.rst
doc/en/monkeypatch.rst
doc/en/naming20.rst
doc/en/nose.rst
doc/en/parametrize.rst
doc/en/plugins.rst
doc/en/projects.rst
doc/en/pytest.ini
doc/en/recwarn.rst
doc/en/requirements.txt
doc/en/setup.rst
doc/en/skipping.rst
doc/en/talks.rst
doc/en/tmpdir.rst
doc/en/unittest.rst
doc/en/usage.rst
doc/en/warnings.rst
doc/en/writing_plugins.rst
doc/en/xunit_setup.rst
doc/en/yieldfixture.rst
doc/en/_templates/globaltoc.html
doc/en/_templates/layout.html
doc/en/_templates/links.html
doc/en/_templates/sidebarintro.html
doc/en/_themes/.gitignore
doc/en/_themes/LICENSE
doc/en/_themes/README
doc/en/_themes/flask_theme_support.py
doc/en/_themes/flask/layout.html
doc/en/_themes/flask/relations.html
doc/en/_themes/flask/theme.conf
doc/en/_themes/flask/static/flasky.css_t
doc/en/announce/index.rst
doc/en/announce/release-2.0.0.rst
doc/en/announce/release-2.0.1.rst
doc/en/announce/release-2.0.2.rst
doc/en/announce/release-2.0.3.rst
doc/en/announce/release-2.1.0.rst
doc/en/announce/release-2.1.1.rst
doc/en/announce/release-2.1.2.rst
doc/en/announce/release-2.1.3.rst
doc/en/announce/release-2.2.0.rst
doc/en/announce/release-2.2.1.rst
doc/en/announce/release-2.2.2.rst
doc/en/announce/release-2.2.4.rst
doc/en/announce/release-2.3.0.rst
doc/en/announce/release-2.3.1.rst
doc/en/announce/release-2.3.2.rst
doc/en/announce/release-2.3.3.rst
doc/en/announce/release-2.3.4.rst
doc/en/announce/release-2.3.5.rst
doc/en/announce/release-2.4.0.rst
doc/en/announce/release-2.4.1.rst
doc/en/announce/release-2.4.2.rst
doc/en/announce/release-2.5.0.rst
doc/en/announce/release-2.5.1.rst
doc/en/announce/release-2.5.2.rst
doc/en/announce/release-2.6.0.rst
doc/en/announce/release-2.6.1.rst
doc/en/announce/release-2.6.2.rst
doc/en/announce/release-2.6.3.rst
doc/en/announce/release-2.7.0.rst
doc/en/announce/release-2.7.1.rst
doc/en/announce/release-2.7.2.rst
doc/en/announce/release-2.8.2.rst
doc/en/announce/release-2.8.3.rst
doc/en/announce/release-2.8.4.rst
doc/en/announce/release-2.8.5.rst
doc/en/announce/release-2.8.6.rst
doc/en/announce/release-2.8.7.rst
doc/en/announce/release-2.9.0.rst
doc/en/announce/release-2.9.1.rst
doc/en/announce/release-2.9.2.rst
doc/en/announce/release-3.0.0.rst
doc/en/announce/release-3.0.1.rst
doc/en/announce/release-3.0.2.rst
doc/en/announce/release-3.0.3.rst
doc/en/announce/release-3.0.4.rst
doc/en/announce/release-3.0.5.rst
doc/en/announce/release-3.0.6.rst
doc/en/announce/release-3.0.7.rst
doc/en/announce/release-3.1.0.rst
doc/en/announce/release-3.1.1.rst
doc/en/announce/release-3.1.2.rst
doc/en/announce/sprint2016.rst
doc/en/example/attic.rst
doc/en/example/conftest.py
doc/en/example/index.rst
doc/en/example/markers.rst
doc/en/example/multipython.py
doc/en/example/nonpython.rst
doc/en/example/parametrize.rst
doc/en/example/pythoncollection.py
doc/en/example/pythoncollection.rst
doc/en/example/reportingdemo.rst
doc/en/example/simple.rst
doc/en/example/special.rst
doc/en/example/xfail_demo.py
doc/en/example/assertion/failure_demo.py
doc/en/example/assertion/test_failures.py
doc/en/example/assertion/test_setup_flow_example.py
doc/en/example/assertion/global_testmodule_config/conftest.py
doc/en/example/assertion/global_testmodule_config/test_hello.py
doc/en/example/costlysetup/conftest.py
doc/en/example/costlysetup/sub1/__init__.py
doc/en/example/costlysetup/sub1/test_quick.py
doc/en/example/costlysetup/sub2/__init__.py
doc/en/example/costlysetup/sub2/test_two.py
doc/en/example/nonpython/__init__.py
doc/en/example/nonpython/conftest.py
doc/en/example/nonpython/test_simple.yml
doc/en/example/py2py3/conftest.py
doc/en/example/py2py3/test_py2.py
doc/en/example/py2py3/test_py3.py
doc/en/img/cramer2.png
doc/en/img/freiburg2.jpg
doc/en/img/gaynor3.png
doc/en/img/keleshev.png
doc/en/img/pullrequest.png
doc/en/img/pylib.png
doc/en/img/pytest1.png
doc/en/img/pytest1favi.ico
doc/en/img/theuni.png
doc/en/proposals/parametrize_with_fixtures.rst
doc/en/test/attic.rst
doc/en/test/config.html
doc/en/test/dist.html
doc/en/test/extend.html
doc/en/test/index.rst
doc/en/test/mission.rst
doc/en/test/test.html
doc/en/test/plugin/cov.rst
doc/en/test/plugin/coverage.rst
doc/en/test/plugin/django.rst
doc/en/test/plugin/figleaf.rst
doc/en/test/plugin/helpconfig.rst
doc/en/test/plugin/index.rst
doc/en/test/plugin/links.rst
doc/en/test/plugin/nose.rst
doc/en/test/plugin/oejskit.rst
doc/en/test/plugin/terminal.rst
doc/en/test/plugin/xdist.rst
extra/get_issues.py
extra/setup-py.test/setup.py
pytest.egg-info/PKG-INFO
pytest.egg-info/SOURCES.txt
pytest.egg-info/dependency_links.txt
pytest.egg-info/entry_points.txt
pytest.egg-info/not-zip-safe
pytest.egg-info/requires.txt
pytest.egg-info/top_level.txt
scripts/call-tox.bat
scripts/check-rst.py
scripts/install-pypy.bat
tasks/__init__.py
tasks/generate.py
tasks/release.minor.rst
tasks/release.patch.rst
tasks/requirements.txt
testing/acceptance_test.py
testing/deprecated_test.py
testing/test_argcomplete.py
testing/test_assertion.py
testing/test_assertrewrite.py
testing/test_cache.py
testing/test_capture.py
testing/test_collection.py
testing/test_compat.py
testing/test_config.py
testing/test_conftest.py
testing/test_doctest.py
testing/test_entry_points.py
testing/test_helpconfig.py
testing/test_junitxml.py
testing/test_mark.py
testing/test_modimport.py
testing/test_monkeypatch.py
testing/test_nose.py
testing/test_parseopt.py
testing/test_pastebin.py
testing/test_pdb.py
testing/test_pluginmanager.py
testing/test_pytester.py
testing/test_recwarn.py
testing/test_resultlog.py
testing/test_runner.py
testing/test_runner_xunit.py
testing/test_session.py
testing/test_skipping.py
testing/test_terminal.py
testing/test_tmpdir.py
testing/test_unittest.py
testing/test_warnings.py
testing/code/test_code.py
testing/code/test_excinfo.py
testing/code/test_source.py
testing/freeze/.gitignore
testing/freeze/create_executable.py
testing/freeze/runtests_script.py
testing/freeze/tox_run.py
testing/freeze/tests/test_doctest.txt
testing/freeze/tests/test_trivial.py
testing/python/approx.py
testing/python/collect.py
testing/python/fixture.py
testing/python/integration.py
testing/python/metafunc.py
testing/python/raises.py
testing/python/setup_only.py
testing/python/setup_plan.py
testing/python/show_fixtures_per_test.py

[coveralls]

Coverage remained the same at 92.133% when pulling 731c35f on nicoddemus:remove-manifest-check into 31b971d on pytest-dev:master.

[shershon1991]

👍