Steam Guard prompt does not work in log file

[CAD97]

Specifically, upon running the build script as py .\Build.py --steam, I get

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Initiating Build Sequence
----------------------------------------------------------------------------------------------------
Pigment Penguins - Step 5: Starting Upload to Steam
----------------------------------------------------------------------------------------------------
Steam Console Client (c) Valve Corporation
-- type 'quit' to exit --
Loading Steam API...OK.
Logging in user 'cdurham_SMU' to Steam Public ...

and the script hangs. When I CTRL-C'd the script, I got the rest of the log:

This computer has not been authenticated for your account using Steam Guard.
Please check your email for the message from Steam, and enter the Steam Guard
 code from that message.
You can also enter this code at any time using 'set_steam_guard_code'
 at the console.
Steam Guard code:FAILED login with result code Account Logon Denied
Traceback (most recent call last):
  File ".\Build.py", line 69, in <module>
    success = upload_to_steam( log_file )
  File "D:\TGP2BuildScripts\Scripts\UploadToSteam.py", line 20, in upload_to_steam
    result = subprocess.run( [steam_dir + steam_cmd, "+login", user_name, user_password, "+run_app_build_http", steam_dir + app_build, "+quit"], stdout=log_file )
  File "C:\Users\Christopher Durham\AppData\Local\Programs\Python\Python38\lib\subprocess.py", line 495, in run
    stdout, stderr = process.communicate(input, timeout=timeout)
  File "C:\Users\Christopher Durham\AppData\Local\Programs\Python\Python38\lib\subprocess.py", line 1020, in communicate
    self.wait()
  File "C:\Users\Christopher Durham\AppData\Local\Programs\Python\Python38\lib\subprocess.py", line 1083, in wait
    return self._wait(timeout=timeout)
  File "C:\Users\Christopher Durham\AppData\Local\Programs\Python\Python38\lib\subprocess.py", line 1361, in _wait
    result = _winapi.WaitForSingleObject(self._handle,
KeyboardInterrupt
src\tier1\fileio.cpp (4914) : Assertion Failed: s_bExit
src\tier1\fileio.cpp (4916) : Assertion Failed: m_vecRegisteredWriters.Count() == 0
src\tier0\threadtools.cpp (3553) : Assertion Failed: Illegal termination of worker thread 'CFileWriterThread'
src\tier0\threadtools.cpp (3553) : Assertion Failed: Illegal termination of worker thread 'Thread(0x5E16A9A8/0x0000079C/0x'
src\tier1\fileio.cpp (4976) : Assertion Failed: CFileWriterThread already exited
src\tier1\fileio.cpp (4976) : Assertion Failed: CFileWriterThread already exited
src\tier1\fileio.cpp (4976) : Assertion Failed: CFileWriterThread already exited

For fire-and-forget, there needs to be an auth solution that doesn't require interactive 2FA through Steam Guard, and I don't know what it is. For interactive use, though, the Steam Guard is definitely problematic.