fix(core): no need to alway perform an os.stat(fd)

Performing an `os.stat(fd)` on Windows platform generate a crash because the "handler is not valid". `select` already handle this possible case and there is no actual need to perform any kind of check before. This was removed, and the linked test slightly changed.

kazoo/handlers/utils.py

@@ -3,7 +3,6 @@
 from collections import defaultdict
 import errno
 import functools
-import os
 import select
 import selectors
 import ssl
@@ -349,7 +348,6 @@ def fileobj_to_fd(fileobj):
             raise TypeError("Invalid file object: " "{!r}".format(fileobj))
     if fd < 0:
         raise TypeError("Invalid file descriptor: {}".format(fd))
-    os.fstat(fd)
     return fd
 
 
@@ -380,7 +378,11 @@ def selector_select(
 
     selector = selectors_module.DefaultSelector()
     for fd, events in fd_events.items():
-        selector.register(fd, events)
+        try:
+            selector.register(fd, events)
+        except (ValueError, OSError) as e:
+            # gevent can raise OSError
+            raise ValueError('Invalid event mask or fd') from e
 
     revents, wevents, xevents = [], [], []
     try:

kazoo/tests/test_selectors_select.py

@@ -3,7 +3,6 @@
  to test the selector_select function.
 """
 
-import errno
 import os
 import socket
 import sys
@@ -41,12 +40,7 @@ def test_errno(self):
         with open(__file__, "rb") as fp:
             fd = fp.fileno()
             fp.close()
-            try:
-                select([fd], [], [], 0)
-            except OSError as err:
-                self.assertEqual(err.errno, errno.EBADF)
-            else:
-                self.fail("exception not raised")
+            self.assertRaises(ValueError, select, [fd], [], [], 0)
 
     def test_returned_list_identity(self):
         # See issue #8329