sqlalchemy >= 0.8 has some incompatible change (might be a small
thing..)
fix a change introduced in 16963190796cba44fb2

see
https://github.com/barsch/seishub.core/commit/16963190796cba44fb2bc5f693f61b5b0945f7ed#commitcomment-5869687
Merge remote-tracking branch 'upstream/master' into quakeml