Region aggregation if region missing

[znicholls]

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• Documentation Added
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Description of PR

Updates pyam so behaviour of check_aggregate_region is sensible even if the region your checking is missing.

[znicholls]

@danielhuppmann @gidden thoughts would be great here. The new tests currently fail in a cryptic way. The question is, if you call check_aggregate_region and the region you're checking isn't there, should an error be raised, a warning or just nothing and None is returned (cause a region can't be wrong if it's not there...)?

[danielhuppmann]

From a quick look, it seems that the command tries to return the object as a pivoted pd.DataFrame (via timeseries()), which doesn't work if the dataframe is empty.

On the question "how do we expect this to behave", I would follow the behaviour in aggregate_region() (log message and empty return):

pyam/pyam/core.py

Line 831 in 127680a

msg = 'cannot aggregate variable `{}` to `{}` because it does not'\

[coveralls]

Coverage decreased (-0.2%) to 87.86% when pulling 2f335a6 on znicholls:region-aggregation-bug into 127680a on IAMconsortium:master.

[coveralls]

Coverage decreased (-0.2%) to 87.873% when pulling cf09266 on znicholls:region-aggregation-bug into dd7ae0c on IAMconsortium:master.

[znicholls]

@danielhuppmann this should be good to go

[danielhuppmann]

thanks @znicholls for improving the user-friendliness of the region.aggregation-checking function!