Hi, all friends!
I want to install graph_tool in Ubuntu 12.04.
I add the source to my sources.list and update the source.
It replys "W: GPG error: http://downloads.skewed.de oneiric Release: The
following signatures couldn't be verified because the public key is
not available: NO_PUBKEY 697EC21F15F95514"
I don't know how to add the public key.
I tried to save
keyfile and "sudo apt-key add keyfile" .
But it says"gpg: no valid OpenPGP data found."
What is this problem? Thank you for your suggestion.
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