Mark some obviously incomplete stubs as incomplete (#3807)

stdlib/2/encodings/__init__.pyi

@@ -1,6 +1,8 @@
 import codecs
 
-import typing
+from typing import Any
 
-def search_function(encoding: str) -> codecs.CodecInfo:
-    ...
+def search_function(encoding: str) -> codecs.CodecInfo: ...
+
+# Explicitly mark this package as incomplete.
+def __getattr__(name: str) -> Any: ...

stdlib/3/encodings/__init__.pyi

@@ -1,3 +1,8 @@
 import codecs
 
+from typing import Any
+
 def search_function(encoding: str) -> codecs.CodecInfo: ...
+
+# Explicitly mark this package as incomplete.
+def __getattr__(name: str) -> Any: ...

third_party/2and3/backports/__init__.pyi

@@ -0,0 +1,4 @@
+from typing import Any
+
+# Explicitly mark this package as incomplete.
+def __getattr__(name: str) -> Any: ...

third_party/2and3/boto/__init__.pyi

@@ -74,3 +74,6 @@ def connect_ec2containerservice(aws_access_key_id: Optional[Any] = ..., aws_secr
 def connect_machinelearning(aws_access_key_id: Optional[Any] = ..., aws_secret_access_key: Optional[Any] = ..., **kwargs): ...
 def storage_uri(uri_str, default_scheme: str = ..., debug: int = ..., validate: bool = ..., bucket_storage_uri_class: Any = ..., suppress_consec_slashes: bool = ..., is_latest: bool = ...): ...
 def storage_uri_for_key(key): ...
+
+# Explicitly mark this package as incomplete.
+def __getattr__(name: str) -> Any: ...

third_party/2and3/boto/ec2/__init__.pyi

@@ -5,3 +5,6 @@ RegionData: Any
 def regions(**kw_params): ...
 def connect_to_region(region_name, **kw_params): ...
 def get_region(region_name, **kw_params): ...
+
+# Explicitly mark this package as incomplete.
+def __getattr__(name: str) -> Any: ...