Drop support for Python 3.5 (#4675)

Python 3.5 EOL was on 2020-09-30.

stdlib/3/collections/__init__.pyi

@@ -3,11 +3,13 @@ import typing
 from typing import (
     AbstractSet,
     Any,
+    AsyncGenerator as AsyncGenerator,
     AsyncIterable as AsyncIterable,
     AsyncIterator as AsyncIterator,
     Awaitable as Awaitable,
     ByteString as ByteString,
     Callable as Callable,
+    Collection as Collection,
     Container as Container,
     Coroutine as Coroutine,
     Dict,
@@ -38,9 +40,6 @@ from typing import (
 
 Set = AbstractSet
 
-if sys.version_info >= (3, 6):
-    from typing import AsyncGenerator as AsyncGenerator, Collection as Collection
-
 _S = TypeVar("_S")
 _T = TypeVar("_T")
 _KT = TypeVar("_KT")
@@ -57,7 +56,7 @@ if sys.version_info >= (3, 7):
         defaults: Optional[Iterable[Any]] = ...,
     ) -> Type[Tuple[Any, ...]]: ...
 
-elif sys.version_info >= (3, 6):
+else:
     def namedtuple(
         typename: str,
         field_names: Union[str, Iterable[str]],
@@ -67,11 +66,6 @@ elif sys.version_info >= (3, 6):
         module: Optional[str] = ...,
     ) -> Type[Tuple[Any, ...]]: ...
 
-else:
-    def namedtuple(
-        typename: str, field_names: Union[str, Iterable[str]], verbose: bool = ..., rename: bool = ...
-    ) -> Type[Tuple[Any, ...]]: ...
-
 class UserDict(MutableMapping[_KT, _VT]):
     data: Dict[_KT, _VT]
     def __init__(self, __dict: Optional[Mapping[_KT, _VT]] = ..., **kwargs: _VT) -> None: ...
@@ -194,9 +188,6 @@ class UserString(Sequence[str]):
     def upper(self: _UserStringT) -> _UserStringT: ...
     def zfill(self: _UserStringT, width: int) -> _UserStringT: ...
 
-# Technically, deque only derives from MutableSequence in 3.5 (before then, the insert and index
-# methods did not exist).
-# But in practice it's not worth losing sleep over.
 class deque(MutableSequence[_T], Generic[_T]):
     @property
     def maxlen(self) -> Optional[int]: ...

stdlib/3/collections/abc.pyi

@@ -1,11 +1,11 @@
-import sys
-
 from . import (
+    AsyncGenerator as AsyncGenerator,
     AsyncIterable as AsyncIterable,
     AsyncIterator as AsyncIterator,
     Awaitable as Awaitable,
     ByteString as ByteString,
     Callable as Callable,
+    Collection as Collection,
     Container as Container,
     Coroutine as Coroutine,
     Generator as Generator,
@@ -19,11 +19,9 @@ from . import (
     MutableMapping as MutableMapping,
     MutableSequence as MutableSequence,
     MutableSet as MutableSet,
+    Reversible as Reversible,
     Sequence as Sequence,
     Set as Set,
     Sized as Sized,
     ValuesView as ValuesView,
 )
-
-if sys.version_info >= (3, 6):
-    from . import AsyncGenerator as AsyncGenerator, Collection as Collection, Reversible as Reversible