Add ``Consider-using-f-string`` checker (#4796)

* Add ``consider-using-f-string`` checker
This adds a checker for normal strings which are formatted
with ``.format()`` or '%'.
The message is a convention to nudge users towards using f-strings.
This closes #3592

* Update pylint code to use f-strings
After adding `consider-using-f-strings` the codebase showed numerous
cases of formatting which could be f-strings.
This commit changes most of these to become f-strings, or adds ignores.

* Apply suggestions from code review

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

3 files changed, 14 insertions, 10 deletions

diff --git a/pylint/testutils/constants.py b/pylint/testutils/constants.py
index fa70d3b57..fc04d927d 100644
--- a/pylint/testutils/constants.py
+++ b/pylint/testutils/constants.py
@@ -7,7 +7,9 @@ import sys
 from os.path import abspath, dirname
 from pathlib import Path
 
-SYS_VERS_STR = "%d%d%d" % sys.version_info[:3]
+SYS_VERS_STR = (
+    "%d%d%d" % sys.version_info[:3]  # pylint: disable=consider-using-f-string
+)
 TITLE_UNDERLINES = ["", "=", "-", "."]
 PREFIX = abspath(dirname(__file__))
 UPDATE_OPTION = "--update-functional-output"
@@ -20,7 +22,7 @@ _MESSAGE = {"msg": r"[a-z][a-z\-]+"}
 #  - followed by a list of bracketed message symbols.
 # Used to extract expected messages from testdata files.
 _EXPECTED_RE = re.compile(
-    r"\s*#\s*(?:(?P<line>[+-]?[0-9]+):)?"
+    r"\s*#\s*(?:(?P<line>[+-]?[0-9]+):)?"  # pylint: disable=consider-using-f-string
     r"(?:(?P<op>[><=]+) *(?P<version>[0-9.]+):)?"
     r"\s*\[(?P<msgs>%(msg)s(?:,\s*%(msg)s)*)]" % _MESSAGE
 )
diff --git a/pylint/testutils/lint_module_test.py b/pylint/testutils/lint_module_test.py
index 8f24daf86..2b5ad2dcb 100644
--- a/pylint/testutils/lint_module_test.py
+++ b/pylint/testutils/lint_module_test.py
@@ -53,8 +53,7 @@ class LintModuleTest:
     def setUp(self):
         if self._should_be_skipped_due_to_version():
             pytest.skip(
-                "Test cannot run with Python %s."
-                % sys.version.split(" ", maxsplit=1)[0]
+                f"Test cannot run with Python {sys.version.split(' ', maxsplit=1)[0]}."
             )
         missing = []
         for requirement in self._test_file.options["requires"]:
@@ -63,7 +62,7 @@ class LintModuleTest:
             except ImportError:
                 missing.append(requirement)
         if missing:
-            pytest.skip("Requires %s to be present." % ",".join(missing))
+            pytest.skip(f"Requires {','.join(missing)} to be present.")
         except_implementations = self._test_file.options["except_implementations"]
         if except_implementations:
             implementations = [i.strip() for i in except_implementations.split(",")]
@@ -74,7 +73,7 @@ class LintModuleTest:
         if excluded_platforms:
             platforms = [p.strip() for p in excluded_platforms.split(",")]
             if sys.platform.lower() in platforms:
-                pytest.skip("Test cannot run on platform %r" % sys.platform)
+                pytest.skip(f"Test cannot run on platform {sys.platform!r}")
 
     def runTest(self):
         self._runTest()
@@ -193,16 +192,19 @@ class LintModuleTest:
     def error_msg_for_unequal_messages(
         self, actual_messages, expected_messages, actual_output: List[OutputLine]
     ):
-        msg = ['Wrong results for file "%s":' % (self._test_file.base)]
+        msg = [f'Wrong results for file "{self._test_file.base}":']
         missing, unexpected = self.multiset_difference(
             expected_messages, actual_messages
         )
         if missing:
             msg.append("\nExpected in testdata:")
-            msg.extend(" %3d: %s" % msg for msg in sorted(missing))
+            msg.extend(
+                " %3d: %s" % msg  # pylint: disable=consider-using-f-string
+                for msg in sorted(missing)
+            )
         if unexpected:
             msg.append("\nUnexpected in testdata:")
-            msg.extend(" %3d: %s" % msg for msg in sorted(unexpected))  # type: ignore
+            msg.extend(" %3d: %s" % msg for msg in sorted(unexpected))  # type: ignore #pylint: disable=consider-using-f-string
         error_msg = "\n".join(msg)
         if self._config and self._config.getoption("verbose") > 0:
             error_msg += "\n\nActual pylint output for this file:\n"
diff --git a/pylint/testutils/reporter_for_tests.py b/pylint/testutils/reporter_for_tests.py
index 45aa63577..b1b7af7e4 100644
--- a/pylint/testutils/reporter_for_tests.py
+++ b/pylint/testutils/reporter_for_tests.py
@@ -32,7 +32,7 @@ class GenericTestReporter(BaseReporter):
         str_message: str = msg.msg
         self.message_ids[msg_id] = 1
         if obj:
-            obj = ":%s" % obj
+            obj = f":{obj}"
         sigle = msg_id[0]
         if linesep != "\n":
             # 2to3 writes os.linesep instead of using