Heroku and Ubuntu

So, I've just spent an hour or two trying to make a new heroku app on my ubuntu machine, and I was getting nowhere.

$git push heroku master
Agent admitted failure to sign using the key.
Permission denied (publickey).
fatal: The remote end hung up unexpectedly

I'd followed all the usual help on stackoverflow and heroku's excellent help section but was making no progress. Until I discovered this. The link to the bug report didn't work for me, but it's clear that I needed to set this SSH_AUTH_SOCK=0 environment variable first:

$export SSH_AUTH_SOCK=0
$git push heroku master

And now we're off!