After downloading SDSS DR7 data products to my local machine, and setting up pipe_base, obs_sdss, etc., and building a repository with genInputRegistry.py, I attempted to run:
% processCcdSdss.py $DATA_DIR/ --id run=1755 filter=r camcol=3 field=411 --output $DEMO_DIR/calexp_dir --configfile $DEMO_DIR/processConfig.py
where $DATA_DIR points to my repository.
The processing terminated (error log attached). At Paul's helpful suggestion, I noticed that the "psField" data product was absent; once supplied the task completed normally. The problem here is that AFAIK there is no tool to validate that a repository is complete and correct for a given camera, and the resulting error message from running the processCcd task is obtuse.