local execution not working anymore

No experiments work anymore. The first block to be processed always throws the same error:

Running `user/integers_add/1' for block `echo'
Start the execution of 'user/integers_add/1'
Block did not execute properly - outputs were reset
  Standard output:
    
  Standard error:
    
  Captured user error:
    File "/home/jae/code/beat.cmdline/src/beat.backend.python/beat/backend/python/loader.py", line 100, in run
        return getattr(obj, method)(*args, **kwargs)
    RuntimeError: done() takes exactly 1 argument (2 given)
  Captured system error:

For reference - I'm using Python 2.7 via a conda environment. All packages are updated, and bob is properly installed. I used this env's python to bootstrap the buildout of beat.cmdline. The nosetests pass fine.