Add stubs for importlib.util (#325)

stdlib/3/importlib/util.pyi

@@ -0,0 +1,47 @@
+import importlib.abc
+import importlib.machinery
+import sys
+import types
+from typing import Any, Callable, List, Optional
+
+def module_for_loader(fxn: Callable[..., types.ModuleType]
+                     ) -> Callable[..., types.ModuleType]: ...
+def set_loader(fxn: Callable[..., types.ModuleType]
+              ) -> Callable[..., types.ModuleType]: ...
+def set_package(fxn: Callable[..., types.ModuleType]
+               ) -> Callable[..., types.ModuleType]: ...
+
+if sys.version_info >= (3, 3):
+    def resolve_name(name: str, package: str) -> str: ...
+
+if sys.version_info >= (3, 4):
+    MAGIC_NUMBER = ... # type: bytes
+
+    def cache_from_source(path: str, debug_override: bool = None, *,
+                          optimization: Any = None) -> str: ...
+    def source_from_cache(path: str) -> str: ...
+    def decode_source(source_bytes: bytes) -> str: ...
+    def find_spec(name: str, package: str = None
+                 ) -> importlib.machinery.ModuleSpec: ...
+    def spec_from_loader(name: str, loader: Optional[importlib.abc.Loader], *,
+                         origin: str = None, loader_state: Any = None,
+                         is_package: bool = None
+                        ) -> importlib.machinery.ModuleSpec: ...
+    def spec_from_file_location(name: str, location: str, *,
+                                loader: importlib.abc.Loader = None,
+                                submodule_search_locations: List[str]=None
+                               ) -> importlib.machinery.ModuleSpec: ...
+
+if sys.version_info >= (3, 5):
+    def module_from_spec(spec: importlib.machinery.ModuleSpec
+                        ) -> types.ModuleType: ...
+
+    class LazyLoader(importlib.abc.Loader):
+        def __init__(self, loader: importlib.abc.Loader) -> None: ...
+        @classmethod
+        def factory(cls, loader: importlib.abc.Loader
+                   ) -> Callable[..., 'LazyLoader']: ...
+        def create_module(self, spec: importlib.machinery.ModuleSpec
+                         ) -> Optional[types.ModuleType]:
+            ...
+        def exec_module(self, module: types.ModuleType) -> None: ...