Problem:
I was getting the following error when I ran `sudo apt-get update`

Reading package lists... Done
W: An error occurred during the signature verification. The repository is not updated and the previous index files will be used. GPG error: https://repo.skype.com/deb stable InRelease: The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository
W: Failed to fetch https://repo.skype.com/deb/dists/stable/InRelease The following signatures were invalid: EXPKEYSIG 1F3045A5DF7587C3 Skype Linux Client Repository
W: Some index files failed to download. They have been ignored, or old ones used instead.

Solution:

  # Delete the old key  $ sudo apt-key del 1F3045A5DF7587C3  # Add the new one  $ curl https://repo.skype.com/data/SKYPE-GPG-KEY | sudo apt-key add -

Source:
https://askubuntu.com/questions/1348146/invalid-signature-from-repo-skype-com-how-can-i-clear-this

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