Fix ASTM import crashing on a sender with null components

[xispa]

Description of the issue/feature this PR addresses

ASTMImporter.get_sender() assumes the (H)eader is present and that each of its three sender components is a string. Neither holds on the wire: ASTM transmits a component the analyzer did not fill as null, and a message can arrive with no header at all.

Every caller then breaks, including one inside this module. get_sender() returning None makes get_instrument_name() and its two siblings raise TypeError: 'NoneType' object is not subscriptable, since they index into the result. A null component makes the AutoImportLog fail to be written:

# importer.py, ASTMImporter.log()
self._importlog.setInterface(", ".join(self.get_sender()))
# TypeError: sequence item 0: expected string, NoneType found

So the message is lost and no log entry records why.

Current behavior before PR

header = self.get_header()
if not header:
    return None
sender = header.get("sender", {})
name = sender.get("name", "")
...

None for a headerless message, and dict.get with a default does not help for a null component: the key is there, holding None, so the default is never reached.

Desired behavior after PR is merged

get_sender() always returns three strings, with surrounding whitespace dropped. Analyzers pad these fields to a fixed width and the Instrument they have to match is configured without the padding, so an unstripped sender silently fails to resolve.

--
I confirm I have tested this PR thoroughly and coded it according to PEP8
and Plone's Python styleguide standards.

[ramonski]

Thanks! Only a small thing while we're already at this code.

[ramonski]

Looks good to me. One small thing in log() while we are at it: with the empty strings we now get an interface like GeneXpert, , for every analyzer that does not send a serial or a version. Could we skip the empty ones there?

sender = filter(None, self.get_sender())
self._importlog.setInterface(", ".join(sender))