assert.PanicsWithError: report error message

[olivergondza]

Summary

Always report error message on PanicsWithError error message mismatch.

Changes

Add Error message field to the failure message, that reports panicErr.Error() IFF it panicked with an error its message is different from expected.

Motivation

Better defect localization in case of nested errors causing panic.

Before:

Error: func (assert.PanicTestFunc)(0x627a80) should panic with error message:	"at the disco"
	Panic value:	&errors.joinError{errs:[]error{(*errors.errorString)(0xc0000a1540), (*errors.errorString)(0xc0000a1550)}}
	Panic stack:	goroutine 19 [running]:
	...

After:

Error: func (assert.PanicTestFunc)(0x627b20) should panic with error message:	"at the disco"
	Panic value:	&errors.joinError{errs:[]error{(*errors.errorString)(0xc000065550), (*errors.errorString)(0xc000065560)}}
	Error message:	"wrapped err msg\nother err msg"
	Panic stack:	goroutine 6 [running]:
	...

Related issues

Closes #1399

[dolmen]

The tests must be fixed to not use assert.CollectT.

[olivergondza]

@dolmen, I have performed the needed refactor and rebased. PTAL.

The captureTestingT could not have been used in the most straightforward way possible, as some of the checks are negative, and test other "labels" than error...

[brackendawson]

I've tested this myself and it works, the change is a worthwhile improvement.

@dolmen are you happy that your comments are addressed?

[brackendawson]

Still LGTM

dolmen's last change requested, to change the variable name mckT to mockT, was completed.