use one() instead of limit(1).first()
use one() instead of limit(1).first()

first() will never raise an exception and thus give None as a result,
but we want SourceError to be raised.

See: http://www.sqlalchemy.org/docs/orm/query.html#sqlalchemy.orm.query.Query.first
And: http://www.sqlalchemy.org/docs/orm/query.html#sqlalchemy.orm.query.Query.one
(transplanted from 629c94efcd3b501a2d3a31566d3e4f927b762169)

SysTheron/adhocracy,liqd/adhocracy,alkadis/vcv,liqd/adhocracy,DanielNeugebauer/adhocracy,liqd/adhocracy,phihag/adhocracy,DanielNeugebauer/adhocracy,SysTheron/adhocracy,phihag/adhocracy,alkadis/vcv,phihag/adhocracy,alkadis/vcv,DanielNeugebauer/adhocracy,phihag/adhocracy,alkadis/vcv,DanielNeugebauer/adhocracy,SysTheron/adhocracy,alkadis/vcv,DanielNeugebauer/adhocracy,liqd/adhocracy,phihag/adhocracy