Require Python 3.6.2 (#5068)

* Bump python_requires to >= 3.6.2

* Import typing names directly
* Use typing.NamedTuple for MessageTest
* Add default value to MessageStyle

* Revert "Add an exception at install for python < 3.6.2 (#5171)"

This reverts commit 37e330cadd12800b484ef89cd599dcb06f1ba539.

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

12 files changed, 34 insertions, 61 deletions

diff --git a/ChangeLog b/ChangeLog
index f58ab1c8d..db75ce76e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -22,6 +22,10 @@ Release date: TBA
 ..
   Put bug fixes that should not wait for a new minor version here
 
+* Require Python ``3.6.2`` to run pylint.
+
+  Closes #5065
+
 ..
   Insert your changelog randomly, it will reduce merge conflicts
   (Ie. not necessarily at the end)
diff --git a/README.rst b/README.rst
index 388a974cc..32871e01c 100644
--- a/README.rst
+++ b/README.rst
@@ -75,7 +75,7 @@ Pylint can be simply installed by running::
 
     pip install pylint
 
-If you are using Python 3.6+, upgrade to get full support for your version::
+If you are using Python 3.6.2+, upgrade to get full support for your version::
 
     pip install pylint --upgrade
 
diff --git a/doc/faq.rst b/doc/faq.rst
index d0a02cf3a..6a401bf25 100644
--- a/doc/faq.rst
+++ b/doc/faq.rst
@@ -48,7 +48,7 @@ supported.
 2.4 What versions of Python is Pylint supporting?
 --------------------------------------------------
 
-The supported running environment since Pylint 2.7.X is Python 3.6+.
+The supported running environment since Pylint 2.12.1 is Python 3.6.2+.
 
 
 3. Running Pylint
diff --git a/doc/whatsnew/2.13.rst b/doc/whatsnew/2.13.rst
index fff0e9318..378b4103b 100644
--- a/doc/whatsnew/2.13.rst
+++ b/doc/whatsnew/2.13.rst
@@ -19,3 +19,7 @@ Extensions
 
 Other Changes
 =============
+
+* Require Python ``3.6.2`` to run pylint.
+
+  Closes #5065
diff --git a/pylint/checkers/strings.py b/pylint/checkers/strings.py
index eb43411de..fb145eaf8 100644
--- a/pylint/checkers/strings.py
+++ b/pylint/checkers/strings.py
@@ -41,7 +41,7 @@ import collections
 import numbers
 import re
 import tokenize
-from typing import TYPE_CHECKING, Iterable
+from typing import Counter, Iterable
 
 import astroid
 from astroid import nodes
@@ -50,9 +50,6 @@ from pylint.checkers import BaseChecker, BaseTokenChecker, utils
 from pylint.checkers.utils import check_messages
 from pylint.interfaces import IAstroidChecker, IRawChecker, ITokenChecker
 
-if TYPE_CHECKING:
-    from typing import Counter  # typing.Counter added in Python 3.6.1
-
 _AST_NODE_STR_TYPES = ("__builtin__.unicode", "__builtin__.str", "builtins.str")
 # Prefixes for both strings and bytes literals per
 # https://docs.python.org/3/reference/lexical_analysis.html#string-and-bytes-literals
@@ -774,8 +771,7 @@ class StringConstantChecker(BaseTokenChecker):
         Args:
           tokens: The tokens to be checked against for consistent usage.
         """
-        # typing.Counter added in Python 3.6.1 so this type hint must be a comment
-        string_delimiters = collections.Counter()  # type: Counter[str]
+        string_delimiters: Counter[str] = collections.Counter()
 
         # First, figure out which quote character predominates in the module
         for tok_type, token, _, _, _ in tokens:
diff --git a/pylint/message/message_id_store.py b/pylint/message/message_id_store.py
index 87e185ac7..1fbe68471 100644
--- a/pylint/message/message_id_store.py
+++ b/pylint/message/message_id_store.py
@@ -1,15 +1,9 @@
 # Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
 # For details: https://github.com/PyCQA/pylint/blob/main/LICENSE
-import sys
-from typing import Dict, List, Optional, Tuple
+from typing import Dict, List, NoReturn, Optional, Tuple
 
 from pylint.exceptions import InvalidMessageError, UnknownMessageError
 
-if sys.version_info >= (3, 6, 2):
-    from typing import NoReturn
-else:
-    from typing_extensions import NoReturn
-
 
 class MessageIdStore:
 
diff --git a/pylint/reporters/text.py b/pylint/reporters/text.py
index 196bee9d8..7ab78e1b8 100644
--- a/pylint/reporters/text.py
+++ b/pylint/reporters/text.py
@@ -59,7 +59,7 @@ class MessageStyle(NamedTuple):
     """The color name (see `ANSI_COLORS` for available values)
     or the color number when 256 colors are available
     """
-    style: Tuple[str, ...]
+    style: Tuple[str, ...] = ()
     """Tuple of style strings (see `ANSI_COLORS` for available values).
     """
 
@@ -264,10 +264,10 @@ class ColorizedTextReporter(TextReporter):
 
     name = "colorized"
     COLOR_MAPPING: ColorMappingDict = {
-        "I": MessageStyle("green", ()),
+        "I": MessageStyle("green"),
         "C": MessageStyle(None, ("bold",)),
         "R": MessageStyle("magenta", ("bold", "italic")),
-        "W": MessageStyle("magenta", ()),
+        "W": MessageStyle("magenta"),
         "E": MessageStyle("red", ("bold",)),
         "F": MessageStyle("red", ("bold", "underline")),
         "S": MessageStyle("yellow", ("inverse",)),  # S stands for module Separator
@@ -326,7 +326,7 @@ class ColorizedTextReporter(TextReporter):
 
     def _get_decoration(self, msg_id: str) -> MessageStyle:
         """Returns the message style as defined in self.color_mapping"""
-        return self.color_mapping.get(msg_id[0]) or MessageStyle(None, ())
+        return self.color_mapping.get(msg_id[0]) or MessageStyle(None)
 
     def handle_message(self, msg: Message) -> None:
         """manage message of different types, and colorize output
diff --git a/pylint/testutils/lint_module_test.py b/pylint/testutils/lint_module_test.py
index 859f1c6c9..8edc63876 100644
--- a/pylint/testutils/lint_module_test.py
+++ b/pylint/testutils/lint_module_test.py
@@ -7,7 +7,8 @@ import platform
 import sys
 from collections import Counter
 from io import StringIO
-from typing import TYPE_CHECKING, Dict, List, Optional, TextIO, Tuple
+from typing import Counter as CounterType
+from typing import Dict, List, Optional, TextIO, Tuple
 
 import pytest
 from _pytest.config import Config
@@ -25,10 +26,7 @@ from pylint.testutils.output_line import OutputLine
 from pylint.testutils.reporter_for_tests import FunctionalTestReporter
 from pylint.utils import utils
 
-if TYPE_CHECKING:
-    from typing import Counter as CounterType  # typing.Counter added in Python 3.6.1
-
-    MessageCounter = CounterType[Tuple[int, str]]
+MessageCounter = CounterType[Tuple[int, str]]
 
 
 class LintModuleTest:
@@ -99,7 +97,7 @@ class LintModuleTest:
         return f"{self._test_file.base} ({self.__class__.__module__}.{self.__class__.__name__})"
 
     @staticmethod
-    def get_expected_messages(stream: TextIO) -> "MessageCounter":
+    def get_expected_messages(stream: TextIO) -> MessageCounter:
         """Parses a file and get expected messages.
 
         :param stream: File-like input stream.
@@ -107,7 +105,7 @@ class LintModuleTest:
         :returns: A dict mapping line,msg-symbol tuples to the count on this line.
         :rtype: dict
         """
-        messages: "MessageCounter" = Counter()
+        messages: MessageCounter = Counter()
         for i, line in enumerate(stream):
             match = _EXPECTED_RE.search(line)
             if match is None:
@@ -133,9 +131,9 @@ class LintModuleTest:
 
     @staticmethod
     def multiset_difference(
-        expected_entries: "MessageCounter",
-        actual_entries: "MessageCounter",
-    ) -> Tuple["MessageCounter", Dict[Tuple[int, str], int]]:
+        expected_entries: MessageCounter,
+        actual_entries: MessageCounter,
+    ) -> Tuple[MessageCounter, Dict[Tuple[int, str], int]]:
         """Takes two multisets and compares them.
 
         A multiset is a dict with the cardinality of the key as the value."""
@@ -162,7 +160,7 @@ class LintModuleTest:
             return open(self._test_file.source, encoding="latin1")
         return open(self._test_file.source, encoding="utf8")
 
-    def _get_expected(self) -> Tuple["MessageCounter", List[OutputLine]]:
+    def _get_expected(self) -> Tuple[MessageCounter, List[OutputLine]]:
         with self._open_source_file() as f:
             expected_msgs = self.get_expected_messages(f)
         if not expected_msgs:
@@ -174,10 +172,10 @@ class LintModuleTest:
             ]
         return expected_msgs, expected_output_lines
 
-    def _get_actual(self) -> Tuple["MessageCounter", List[OutputLine]]:
+    def _get_actual(self) -> Tuple[MessageCounter, List[OutputLine]]:
         messages: List[Message] = self._linter.reporter.messages
         messages.sort(key=lambda m: (m.line, m.symbol, m.msg))
-        received_msgs: "MessageCounter" = Counter()
+        received_msgs: MessageCounter = Counter()
         received_output_lines = []
         for msg in messages:
             assert (
@@ -204,8 +202,8 @@ class LintModuleTest:
 
     def error_msg_for_unequal_messages(
         self,
-        actual_messages: "MessageCounter",
-        expected_messages: "MessageCounter",
+        actual_messages: MessageCounter,
+        expected_messages: MessageCounter,
         actual_output: List[OutputLine],
     ) -> str:
         msg = [f'Wrong results for file "{self._test_file.base}":']
@@ -250,7 +248,7 @@ class LintModuleTest:
 
     def _check_output_text(
         self,
-        _: "MessageCounter",
+        _: MessageCounter,
         expected_output: List[OutputLine],
         actual_output: List[OutputLine],
     ) -> None:
diff --git a/pylintrc b/pylintrc
index 3005cc676..a38a35aed 100644
--- a/pylintrc
+++ b/pylintrc
@@ -44,7 +44,7 @@ unsafe-load-any-extension=no
 extension-pkg-allow-list=
 
 # Minimum supported python version
-py-version = 3.6
+py-version = 3.6.2
 
 
 [MESSAGES CONTROL]
diff --git a/requirements_test_pre_commit.txt b/requirements_test_pre_commit.txt
index cf351dde3..1ce76e355 100644
--- a/requirements_test_pre_commit.txt
+++ b/requirements_test_pre_commit.txt
@@ -1,6 +1,6 @@
 # Everything in this file should reflect the pre-commit configuration
 # in .pre-commit-config.yaml
-black==21.11b1;python_full_version>="3.6.2"
+black==21.11b1
 flake8==4.0.1
 flake8-typing-imports==1.10.1
 isort==5.10.1
diff --git a/setup.py b/setup.py
index a6ee6b4aa..606849326 100644
--- a/setup.py
+++ b/setup.py
@@ -1,20 +1,3 @@
-import sys
-
 from setuptools import setup
 
-
-class PylintIncompatiblePythonError(Exception):
-    def __init__(self) -> None:
-        super().__init__(
-            "The last version compatible with Python <= 3.6.2 is pylint '2.9.3'. "
-            f"You're using {'.'.join([str(v) for v in sys.version_info[:3]])}. "
-            "Please install pylint 2.9.3 explicitly or upgrade your python interpreter "
-            "to at least 3.6.2. Remember that Python 3.6 end life is December 2021. "
-            "See https://github.com/PyCQA/pylint/issues/5065 for more detail."
-        )
-
-
-if sys.version_info < (3, 6, 2):
-    raise PylintIncompatiblePythonError()
-
 setup()
diff --git a/tests/lint/test_pylinter.py b/tests/lint/test_pylinter.py
index 74ddde2ed..9d6695a25 100644
--- a/tests/lint/test_pylinter.py
+++ b/tests/lint/test_pylinter.py
@@ -1,5 +1,4 @@
-import sys
-from typing import Any
+from typing import Any, NoReturn
 from unittest.mock import patch
 
 from astroid import AstroidBuildingError
@@ -9,11 +8,6 @@ from pytest import CaptureFixture
 from pylint.lint.pylinter import PyLinter
 from pylint.utils import FileState
 
-if sys.version_info >= (3, 6, 2):
-    from typing import NoReturn
-else:
-    from typing_extensions import NoReturn
-
 
 def raise_exception(*args: Any, **kwargs: Any) -> NoReturn:
     raise AstroidBuildingError(modname="spam")