Unable to verify Python files

[george]

Hello,

I'm trying to verify the downloaded Python 3.9.1 files before I install them...

I created a new folder and downloaded these two files to it:

Python-3.9.1.tar.xz
Python-3.9.1.tar.xz.asc

I also downloaded and imported the public key to verify the files.

According to the Python website in order to verify the download I need to run this command:

gpg --verify Python-3.9.1.tar.xz.asc

I get the following message when I run the command:

gpg: Signature made Mon 07 Dec 2020 03:37:32 PM MST
gpg: using RSA key E3FF2839C048B25C084DEBE9B26995E310250568
gpg: Can't check signature: No public key

When I run gpg --list-keys I see this key info:

pub rsa4096 2015-05-11 [SC] [expires: 2025-05-11]
E3FF2839C048B25C084DEBE9B26995E310250568
uid [ unknown] Łukasz Langa (GPG langa.pl) <[email protected]>
uid [ unknown] Łukasz Langa (Work e-mail account) <[email protected]>
uid [ unknown] [jpeg image of size 24479]
sub rsa4096 2015-05-11 [E] [expires: 2025-05-11]

Can you someone please explain to me why I'm getting the gpg: Can't check signature: No public key error?

Thank you