We need to create a copy of the head_parsers.
Otherwise the self.value_formats contains just a reference to
head_parsers.
But the self.value_formats is modified in the _parse_values, causing
invalid values in the head_parsers list.
At least the BE and the NL DSMR devices use MBUS.
Therefore we make the MBUS obis reference generic, and convert the V5
telegram to use MBUS values.
Finally set self.maxDiff = None to have a full test output on some
tests.
Sometimes peak usage is not yet visible in the 13 months history code.
It gives a 0.0kW value with timestamp (632525252525W).
Also the peak usage value can be invalid, handle this case also.
Sometimes the timestamp in the DSMR message is invalid (when no data
read read from the mbus meter?), and then parsing fails.
Fixing this by handling the exception and returning None for invalid
timestamps. Fixes: #120
dupondje