Unclear messaging on metrics_collector errors

[jk1066]

to_frame in the metrics collector object is built on a try/except, with unclear messaging whether the logging errors are actually a problem or what would cause them to occur. For example, line 76:

except AssertionError as e:
           logging.error('got error: {}, setting df to be empty!'.format(e))
           df = pd.DataFrame(columns=np.concatenate([idx_columns, self.columns]))

Can result in this error message:

./DSO_5/Substation_5_log.txt:ERROR: metrics_collector: 77: got error: len(data.shape[2:]) = 1 should be == len(shape) = 2, setting df to be empty!

Which seems like a problem. But the simulation continues and metrics continue to be written.