Behavior if dict key is not found in config
We currently found two bugs of the same sort (looks like 'typos'), the wrong use of dict.get(), namely
`value = dict.get(key_a, key_b)`
which should be
`value = dict.get(key_a, value_b)`
Example from fit_toys.py, L151:
`nfits = config['fit'].get('nfits-per-job', 'nfits')`
Which I converted to
`nfits = config['fit'].get('nfits-per-job', config['fit']['nfits'])`
so it reflects the expected behavior as long as the key is present and raises a key error if it is missing in the config. This is contrary to other examples I found in the code, where with .get a real default value is provided.
Question: how do we handle the missing parameters? Are they already catched before? Or should an explicit ConfigError be raised here?
I can look for further occurrences and fix them as soon as the strategy is clear.