fix instance Warning state behavior in GUI

[davidlatwe]

Found that instance's warning state only take effect from the last plugin.

• If warning was not emitted by the last plugin, then it will be override by error or (it should be) success.

  

• If warning was emitted by the last plugin, instance's error state will be override.

  

---

Thought this should not be a normal instance item log level behavior, I added persistWarning into item-model to keep the warning state for instance item, and reset warning state if that instance got error.

---

Simple test case I used

[davidlatwe]

Since QML doesn't count the warning amount, so keep it count them as passed.

[mottosso]

Well spotted!

[davidlatwe]

Can I also fix my last PR's pep8 issue ?

[mottosso]

Excellent, this looks good!

In the future, it'd be better to put a commit message that describes what the change does, rather than a series of versions. Think of each commit as a self-contained whole, something you might one day want to revert, or cherry-pick onto a different branch. And consider what it will look like in midst other commits, here.

For now, this is fine. Just a minor tweak for future PRs.

[mottosso]

Thanks @davidlatwe!

[davidlatwe]

In the future, it'd be better to put a commit message that describes what the change does

Sure, will do !