Show error output from Psalm as part of report about each killed mutant.

[bdsl]

When a mutant is killed by PHPUnit the output from PHPUnit is included in some of the reports Infection generates, which is helpful to understand how the test relates to the mutant. Currently when a mutant is killed by a Psalm check the output field is left blank.

I think it would be useful to be able to see the message(s) from Psalm in the report, and fairly straightforward to implement that inside this plugin's code. I actually did a rough version of it on my copy which is how I learned about issue #484 .

I'll try and make a PR for this if maintainers her think it would be useful.

[Ocramius]

Currently when a mutant is killed by a Psalm check the output field is left blank.

I don't think output capturing was part of the upstream project when this was designed, so do feel free to introduce it 👍

[bdsl]

Thanks, I'll try and make a PR in the next few days or weeks.