ZeroDivisionError if an on-demand table is picked up by table regex configuration

[dtrsan]

It looks like on-demand tables have ProvisionedThroughputs always set to 0. If your table regex accidentally picks up on-demand table, Dynamic DynamoDB will throw ZeroDivisionError exceptions.

It blows up here after get_provisioned_table_read_units returns 0. It could happen for write units too and probably for GSI r/w units too.

dynamic-dynamodb - ERROR - float division by zero
Traceback (most recent call last):
File "/usr/lib/python2.7/site-packages/dynamic_dynamodb/__init__.py", line 101, in main
execute()
File "/usr/lib/python2.7/site-packages/dynamic_dynamodb/__init__.py", line 134, in execute
table_num_consec_write_checks)
File "/usr/lib/python2.7/site-packages/dynamic_dynamodb/core/table.py", line 37, in ensure_provisioning
__ensure_provisioning_alarm(table_name, key_name)
File "/usr/lib/python2.7/site-packages/dynamic_dynamodb/core/table.py", line 961, in __ensure_provisioning_alarm
table_name, lookback_window_start, lookback_period)
File "/usr/lib/python2.7/site-packages/dynamic_dynamodb/statistics/table.py", line 49, in get_consumed_read_units_percent
float(table_read_units) * 100)
ZeroDivisionError: float division by zero

Maybe just to ignore on-demand tables and log a warning that a table is ignored instead of throwing ZeroDivisionError.