In ced21f5e1a, fetchurl has changed into
fetchPypi, but the upstream tarball is actually a tar.bz2 archive but by
default fetchPypi uses "tar.gz" as its extension.
The sha256 however is still the same.
Signed-off-by: aszlig <aszlig@nix.build>
Cc: @FRidh
c15e6fd3fd