"spack commands --update-completion"

lib/spack/llnl/util/tty/log.py

@@ -938,8 +938,7 @@ def _writer_daemon(stdin_multiprocess_fd, read_multiprocess_fd, write_fd, echo,
     # write_fd to terminate the reading loop, so we close the file descriptor
     # here. Forking is the process spawning method everywhere except Mac OS
     # for Python >= 3.8 and on Windows
-    if sys.version_info < (3, 8) \
-            or sys.platform not in ['darwin', 'cygwin']:
+    if sys.version_info < (3, 8) or sys.platform != 'darwin':
         os.close(write_fd)
 
     # Use line buffering (3rd param = 1) since Python 3 has a bug