typing: add a fake `__init__()` to bytestr to distract pytype I'm not sure what changed before pytype 09-09-2021 (from 04-15-2021), but these started getting flagged. This wrapping an exception in a `bytestr` pattern has been flagged before, and I've fixed it then with `stringutil.forcebytestr()`. But that doesn't work here, because it would create a circular import. I suspect the issue is `bytes.__new__()` wants `Iterable[int]`, so it just assumes the subclass will also take that. The referenced pytype bug isn't an exact match, but seems related and the suggested workaround helps. The specific warnings fixed are: File "/mnt/c/Users/Matt/hg/mercurial/encoding.py", line 212, in tolocal: Function bytestr.__init__ was called with the wrong arguments [wrong-arg-types] Expected: (self, ints: Iterable[int]) Actually passed: (self, ints: LookupError) Attributes of protocol Iterable[int] are not implemented on LookupError: __iter__ Called from (traceback): line 353, in current file File "/mnt/c/Users/Matt/hg/mercurial/encoding.py", line 240, in fromlocal: Function bytestr.__init__ was called with the wrong arguments [wrong-arg-types] Expected: (self, ints: Iterable[int]) Actually passed: (self, ints: UnicodeDecodeError) Attributes of protocol Iterable[int] are not implemented on UnicodeDecodeError: __iter__ Differential Revision: https://phab.mercurial-scm.org/D11466

--- a/mercurial/pycompat.py	Mon Sep 20 15:51:23 2021 -0400
+++ b/mercurial/pycompat.py	Tue Sep 21 00:16:35 2021 -0400
@@ -222,6 +222,15 @@
         >>> assert type(t) is bytes
         """
 
+        # Trick pytype into not demanding Iterable[int] be passed to __new__(),
+        # since the appropriate bytes format is done internally.
+        #
+        # https://github.com/google/pytype/issues/500
+        if TYPE_CHECKING:
+
+            def __init__(self, s=b''):
+                pass
+
         def __new__(cls, s=b''):
             if isinstance(s, bytestr):
                 return s