Custodian is a simple, robust and flexible just-in-time (JIT) job management framework written in Python. Using custodian, you can create wrappers that perform error checking, job management and error recovery. It has a simple plugin framework that allows you to develop specific job management workflows for different applications. The current version of Custodian also comes with sub-packages for error handling for Vienna Ab Initio Simulation Package (VASP), NwChem and QChem calculations.