What is the NPOLICY file descriptor type in MacOS Mojave 10.14?

Hello, I am seeing this error triggered by my app in the Console App in Mojave nw_path_close_fd Failed to close guarded necp fd 6 [9: Bad file descriptor].

The app basically makes an HTTP request and then runs the ls command (any command triggers it). In the console app the error is logged with the PID of the child process.

I have narrowed it down to a file descriptor of type NPOLICY that opens whenever my app makes a request to a site such as apple.com and then runs the command. But the file descriptor doesn't open for other sites such as yahoo.com.

Anyone know what the NPOLICY file descriptor type is and why it is opened for some URLs and not others?
What is the NPOLICY file descriptor type in MacOS Mojave 10.14?
 
 
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