add stub for importlib.resources (#1993)

Part of #1965

stdlib/3.7/importlib/resources.pyi

@@ -0,0 +1,22 @@
+import os
+
+from pathlib import Path
+from types import ModuleType
+from typing import ContextManager, Iterator, Union, BinaryIO, TextIO
+
+Package = Union[str, ModuleType]
+Resource = Union[str, os.PathLike]
+
+def open_binary(package: Package, resource: Resource) -> BinaryIO: ...
+def open_text(package: Package,
+              resource: Resource,
+              encoding: str = ...,
+              errors: str = ...) -> TextIO: ...
+def read_binary(package: Package, resource: Resource) -> bytes: ...
+def read_text(package: Package,
+              resource: Resource,
+              encoding: str = ...,
+              errors: str = ...) -> str: ...
+def path(package: Package, resource: Resource) -> ContextManager[Path]: ...
+def is_resource(package: Package, name: str) -> bool: ...
+def contents(package: Package) -> Iterator[str]: ...

stdlib/3/importlib/abc.pyi

@@ -1,7 +1,8 @@
 from abc import ABCMeta, abstractmethod
+import os
 import sys
 import types
-from typing import Any, Mapping, Optional, Sequence, Tuple, Union
+from typing import Any, IO, Iterator, Mapping, Optional, Sequence, Tuple, Union
 
 # Loader is exported from this module, but for circular import reasons
 # exists in its own stub file (with ModuleSpec and ModuleType).
@@ -87,3 +88,16 @@ if sys.version_info >= (3, 3):
         def __init__(self, fullname: str, path: _Path) -> None: ...
         def get_data(self, path: _Path) -> bytes: ...
         def get_filename(self, fullname: str) -> _Path: ...
+
+if sys.version_info >= (3, 7):
+    _PathLike = Union[bytes, str, os.PathLike[Any]]
+
+    class ResourceReader(metaclass=ABCMeta):
+        @abstractmethod
+        def open_resource(self, resource: _PathLike) -> IO[bytes]: ...
+        @abstractmethod
+        def resource_path(self, resource: _PathLike) -> str: ...
+        @abstractmethod
+        def is_resource(self, name: str) -> bool: ...
+        @abstractmethod
+        def contents(self) -> Iterator[str]: ...