https://www.torproject.org/docs/debian.html.en lists 0.3.4 repo but only 0.3.5 is there
Compare https://deb.torproject.org/torproject.org/dists/ with https://www.torproject.org/docs/debian.html.en
The webpage has 0.3.4 experimental in the dropdown; but only 0.3.5 experimental is on deb.tpo