add longrepr from plugin tests

[helpmefindaname]

According to the pytest reference report.longrepr can be either a an object holding a reprcrash, a tuple containing filename linenumber and message in the respective order or a plain string containing a raw message.

The latter is the way plugins like pytest-flake8 or pytest-mypy Create their error messages. I propose adding the full context there, as only the report.head_line or item.name can lead to rather confusing outcomes

I guess it would be even nicer to create multiple annotations per error, but then this plugin's code base would be too dependent on certain other plugins. Having the errors listed at the start of the file should be enough.

[utgwkk]

@helpmefindaname I fixed CI in #51. Could you update this branch?

[helpmefindaname]

Thanks for the fast response, I have updated the branch now

[utgwkk]

I have just published version 0.1.7 including this patch. Thank you for your contribution! @helpmefindaname