Create autoreport even when non-numeric value exists in numeric field

[jnm]

Quick summary

Because the autoreport in KPI is displayed alongside

Warning
This is an automated report based on raw data submitted to this project. Please conduct proper data cleaning prior to using the graphs and figures used on this page.

...we should treat invalid responses as if they were blank when calculating statistics.

Explanation

This problem is a manifestation of #151. Consider a form with two versions:

Version 1

type	name	label
start	start
end	end
text	i_started_life_as_a_text_question	i started life as a text question

Version 2

type	name	label
start	start
end	end
integer	i_started_life_as_a_text_question	i started life as a text question

If I submit hello while version 1 is deployed and 123 while version 2 is deployed, the autoreport will fail at

formpack/src/formpack/schema/fields.py

Lines 513 to 517 in d4e4ce0

	def parse_values(self, raw_values):
	if self.data_type == "integer":
	yield int(raw_values)
	else:
	yield float(raw_values)

ValueError: invalid literal for int() with base 10: 'hello'
  <snip>
  File "kobo/apps/reports/report_data.py", line 178, in data_by_identifiers
    split_by=split_by)
  File "formpack/reporting/autoreport.py", line 209, in get_stats
    return self._calculate_stats(submissions, fields, self.versions, lang)
  File "formpack/reporting/autoreport.py", line 73, in _calculate_stats
    values = list(field.parse_values(raw_value))
  File "formpack/schema/fields.py", line 515, in parse_values
    yield int(raw_values)