Coastal Blue Carbon error with just one snapshot year

[emlys]

A user reported an error in CBC:

File “natcap\invest\coastal_blue_carbon\coastal_blue_carbon.py”, line 956, in execute
KeyError: ‘soil’

The model is expecting there to be more than one snapshot year, ultimately causing this KeyError. A possible workaround is to set the Analysis Year to the snapshot year + 1, but that shouldn't be necessary. @phargogh confirmed over slack that CBC should work with just one snapshot year, though results will be very limited.

[emlys]

On the team call today, we agreed to disallow running the model with just one year. Without at least one year for carbon to accumulate, the model is pretty useless. A user trying to run with just one year probably misunderstands something.