Clean up a few Python 2 remnants (#8452)

CONTRIBUTING.md

@@ -435,8 +435,6 @@ Some further tips for good type hints:
 * avoid invariant collection types (`list`, `dict`) in argument
   positions, in favor of covariant types like `Mapping` or `Sequence`;
 * avoid union return types: https://github.com/python/mypy/issues/1693;
-* in Python 2, whenever possible, use `unicode` if that's the only
-  possible type, and `Text` if it can be either `unicode` or `bytes`;
 * use platform checks like `if sys.platform == 'win32'` to denote
   platform-dependent APIs;
 * use mypy error codes for mypy-specific `# type: ignore` annotations,

pyproject.toml

@@ -28,22 +28,4 @@ extra_standard_library = [
     "genericpath",
     "opcode",
     "pyexpat",
-    # Python 2 modules
-    "__builtin__",
-    "cookielib",
-    "cStringIO",
-    "httplib",
-    "mimetools",
-    "rfc822",
-    "thread",
-    "urllib2",
-    "urlparse",
-    "BaseHTTPServer",
-    "Queue",
-    "SimpleHTTPServer",
-    "SocketServer",
-    "StringIO",
-    "UserDict",
-    "UserList",
-    "UserString",
 ]

stdlib/codecs.pyi

@@ -75,7 +75,7 @@ class _Stream(_WritableStream, _ReadableStream, Protocol): ...
 # bytes is the raw form and str is the cooked form.
 # In the long run, both should become template parameters maybe?
 # There *are* bytes->bytes and str->str encodings in the standard library.
-# They are much more common in Python 2 than in Python 3.
+# They were much more common in Python 2 than in Python 3.
 
 class _Encoder(Protocol):
     def __call__(self, input: str, errors: str = ...) -> tuple[bytes, int]: ...  # signature of Codec().encode

stubs/croniter/croniter/croniter.pyi

@@ -50,7 +50,7 @@ class croniter(Iterator[Any]):
         day_or: bool = ...,
         max_years_between_matches: int | None = ...,
         is_prev: bool = ...,
-        hash_id: str | bytes | None = ...,  # unicode not accepted on python 2
+        hash_id: str | bytes | None = ...,
     ) -> None: ...
     # Most return value depend on ret_type, which can be passed in both as a method argument and as
     # a constructor argument.

tests/pytype_test.py

@@ -4,8 +4,7 @@
 Depends on pytype being installed.
 
 If pytype is installed:
-    1. For every pyi, do nothing if it is in pytype_exclude_list.txt or is
-       Python 2-only.
+    1. For every pyi, do nothing if it is in pytype_exclude_list.txt.
     2. Otherwise, call 'pytype.io.parse_pyi'.
 Option two will load the file and all the builtins, typeshed dependencies. This
 will also discover incorrect usage of imported modules.