Create stubs for the secrets module in Python 3.6

stdlib/3.6/secrets.pyi

@@ -0,0 +1,14 @@
+# Stubs for secrets (Python 3.6)
+
+from typing import Optional, Sequence, TypeVar
+from hmac import compare_digest as compare_digest
+from random import SystemRandom as SystemRandom
+
+_T = TypeVar('_T')
+
+def randbelow(exclusive_upper_bound: int) -> int: ...
+def randbits(k: int) -> int: ...
+def choice(seq: Sequence[_T]) -> _T: ...
+def token_bytes(nbytes: Optional[int]) -> bytes: ...
+def token_hex(nbytes: Optional[int]) -> str: ...
+def token_urlsafe(nbytes: Optional[int]) -> str: ...