Throw an exception on an unrecognized provider
Throw an exception on an unrecognized provider

mathstuf/sprokit,linus-sherrill/sprokit,Kitware/sprokit,linus-sherrill/sprokit,Kitware/sprokit,linus-sherrill/sprokit,mathstuf/sprokit,Kitware/sprokit,linus-sherrill/sprokit,Kitware/sprokit,mathstuf/sprokit,mathstuf/sprokit