Add flake8-typing-imports

[kasium]

The idea to include this plugin comes from #1095 . In short, flake8-typing-imports checks if a import from typing is possible in a certain python version.

I ran the plugin in your code base, and it's NOT compatible with <= 3.6.2. You use NamingTuple with defaults and NoReturn which were added in later patches of 3.6. To let in still run I set the minimum version to 3.7.0.

This means, that either we should fix the issues or gitpython needs to drop the support for this version which is anyway deprecated.
This plugin will hopefully prevent that any new issues are added

[kasium]

Output for 3.6.0

git/types.py:7:1: TYP001 guard import by `if TYPE_CHECKING:`: NoReturn (not in 3.6.0, 3.6.1)
from typing import (Callable, Dict, NoReturn, Sequence, Tuple, Union, Any, Iterator,       # noqa: F401
^
git/index/base.py:70:1: TYP001 guard import by `if TYPE_CHECKING:`: NoReturn (not in 3.6.0, 3.6.1)
from typing import (Any, BinaryIO, Callable, Dict, IO, Iterable, Iterator, List, NoReturn,
^
git/index/typ.py:69:5: TYP005 NamedTuple does not support defaults in 3.6.0
    ctime_bytes: bytes = pack(">LL", 0, 0)
    ^
git/index/typ.py:70:5: TYP005 NamedTuple does not support defaults in 3.6.0
    mtime_bytes: bytes = pack(">LL", 0, 0)
    ^
git/index/typ.py:71:5: TYP005 NamedTuple does not support defaults in 3.6.0
    dev: int = 0
    ^
git/index/typ.py:72:5: TYP005 NamedTuple does not support defaults in 3.6.0
    inode: int = 0
    ^
git/index/typ.py:73:5: TYP005 NamedTuple does not support defaults in 3.6.0
    uid: int = 0
    ^
git/index/typ.py:74:5: TYP005 NamedTuple does not support defaults in 3.6.0
    gid: int = 0
    ^
git/index/typ.py:75:5: TYP005 NamedTuple does not support defaults in 3.6.0
    size: int = 0
    ^
git/objects/util.py:25:1: TYP001 guard import by `if TYPE_CHECKING:`: Deque (not in 3.6.0)
from typing import (Any, Callable, Deque, Iterator, NamedTuple, overload, Sequence,
^
git/refs/remote.py:12:1: TYP001 guard import by `if TYPE_CHECKING:`: NoReturn (not in 3.6.0, 3.6.1)
from typing import Any, Iterator, NoReturn, Union, TYPE_CHECKING
^
4     TYP001 guard import by `if TYPE_CHECKING:`: NoReturn (not in 3.6.0, 3.6.1)
7     TYP005 NamedTuple does not support defaults in 3.6.0
11

[Yobmod]

I've set the checks to run :)
Seems useful already!

So we have to decide: Drop 3.6 now, or i'll pull out NamedTuple defaults (there are only a couple of uses) for now.
NoReturn and Deque are available in typing_extensions, so that can be easily fixed.

I was planning to wait until 3.10 released to drop 3.6.
But I see it had it's final release this June and i have noticed big packages already dropping it (numpy and pandas and therefore most of scientific packages).
(Copying to issue for disucssion)