Add option to silence warnings related to deprecation of Python versions (#6739)

* Add option to silence warnings related to deprecation of Python versions

* Move skip_if_python2 and skip_if_not_python2 decorator declaratios to test/lib/__init__.py and use them in test_warning.py

* Add tests to ensure that python version deprecation warning is shown correctly and can be silenced by a flag.

* Add new test to ensure that --no-python-version-warning flag does nothing if python version is not 2

Author: victorvpaulo

news/6673.feature

@@ -0,0 +1,2 @@
+Add option ``--no-python-version-warning`` to silence warnings
+related to deprecation of Python versions.

src/pip/_internal/cli/base_command.py

@@ -122,7 +122,10 @@ def _main(self, args):
             user_log_file=options.log,
         )
 
-        if sys.version_info[:2] == (2, 7):
+        if (
+            sys.version_info[:2] == (2, 7) and
+            not options.no_python_version_warning
+        ):
             message = (
                 "A future version of pip will drop support for Python 2.7. "
                 "More details about Python 2 support in pip, can be found at "

src/pip/_internal/cli/cmdoptions.py

@@ -891,6 +891,16 @@ def check_list_path_option(options):
         )
 
 
+no_python_version_warning = partial(
+    Option,
+    '--no-python-version-warning',
+    dest='no_python_version_warning',
+    action='store_true',
+    default=False,
+    help='Silence deprecation warnings for upcoming unsupported Pythons.',
+)  # type: Callable[..., Option]
+
+
 ##########
 # groups #
 ##########
@@ -918,6 +928,7 @@ def check_list_path_option(options):
         no_cache,
         disable_pip_version_check,
         no_color,
+        no_python_version_warning,
     ]
 }  # type: Dict[str, Any]
 

tests/functional/test_install.py

@@ -9,7 +9,6 @@
 from os.path import curdir, join, pardir
 
 import pytest
-from pip._vendor.six import PY2
 
 from pip import __version__ as pip_current_version
 from pip._internal.cli.status_codes import ERROR, SUCCESS
@@ -27,6 +26,8 @@
     pyversion,
     pyversion_tuple,
     requirements_file,
+    skip_if_not_python2,
+    skip_if_python2,
 )
 from tests.lib.filesystem import make_socket_file
 from tests.lib.local_repos import local_checkout
@@ -38,9 +39,6 @@
     server_running,
 )
 
-skip_if_python2 = pytest.mark.skipif(PY2, reason="Non-Python 2 only")
-skip_if_not_python2 = pytest.mark.skipif(not PY2, reason="Python 2 only")
-
 
 @pytest.mark.parametrize('command', ('install', 'wheel'))
 @pytest.mark.parametrize('variant', ('missing_setuptools', 'bad_setuptools'))

tests/functional/test_warning.py

@@ -1,7 +1,10 @@
+import platform
 import textwrap
 
 import pytest
 
+from tests.lib import skip_if_not_python2, skip_if_python2
+
 
 @pytest.fixture
 def warnings_demo(tmpdir):
@@ -28,3 +31,39 @@ def test_deprecation_warnings_can_be_silenced(script, warnings_demo):
     script.environ['PYTHONWARNINGS'] = 'ignore'
     result = script.run('python', warnings_demo)
     assert result.stderr == ''
+
+
+DEPRECATION_TEXT = "drop support for Python 2.7"
+CPYTHON_DEPRECATION_TEXT = "January 1st, 2020"
+
+
+@skip_if_python2
+def test_version_warning_is_not_shown_if_python_version_is_not_2(script):
+    result = script.pip("debug", allow_stderr_warning=True)
+    assert DEPRECATION_TEXT not in result.stderr, str(result)
+    assert CPYTHON_DEPRECATION_TEXT not in result.stderr, str(result)
+
+
+@skip_if_python2
+def test_flag_does_nothing_if_python_version_is_not_2(script):
+    script.pip("list", "--no-python-version-warning")
+
+
+@skip_if_not_python2
+def test_version_warning_is_shown_if_python_version_is_2(script):
+    result = script.pip("debug", allow_stderr_warning=True)
+    assert DEPRECATION_TEXT in result.stderr, str(result)
+    if platform.python_implementation() == 'CPython':
+        assert CPYTHON_DEPRECATION_TEXT in result.stderr, str(result)
+    else:
+        assert CPYTHON_DEPRECATION_TEXT not in result.stderr, str(result)
+
+
+@skip_if_not_python2
+def test_version_warning_is_not_shown_when_flag_is_passed(script):
+    result = script.pip(
+        "debug", "--no-python-version-warning", allow_stderr_warning=True
+    )
+    assert DEPRECATION_TEXT not in result.stderr, str(result)
+    assert CPYTHON_DEPRECATION_TEXT not in result.stderr, str(result)
+    assert "--no-python-version-warning" not in result.stderr

tests/lib/__init__.py

@@ -11,6 +11,7 @@
 from textwrap import dedent
 
 import pytest
+from pip._vendor.six import PY2
 from scripttest import FoundDir, TestFileEnvironment
 
 from pip._internal.index.collector import LinkCollector
@@ -1047,3 +1048,7 @@ def need_mercurial(fn):
     return pytest.mark.mercurial(need_executable(
         'Mercurial', ('hg', 'version')
     )(fn))
+
+
+skip_if_python2 = pytest.mark.skipif(PY2, reason="Non-Python 2 only")
+skip_if_not_python2 = pytest.mark.skipif(not PY2, reason="Python 2 only")