Fix stackoverflow in ArgumentsAreDifferent reporting

[TimvdLippe]

When using Mockito without opentest4j, reporting an
ArgumentsAreDifferent exception would throw a StackOverflowError when
attempting to obtain the message from the exception.

The root problem was that super.toString() would call its own
getMessage(). Instead, we should obtain the message from the super, to
avoid the circular call.

[TimvdLippe]

Note that I tried to create a regression test for this, but sadly was unable to. To make the integration test work, we would need to exclude both opentest4j and junit4. While that would technically be possible, Gradle wouldn't be able to pick up a test that is not annotated with @Test. I also tried using JUnit5, but they have a transitive dependency on opentest4j. Any attempt to exclude the transitive dependency causes the Gradle task to crash. I have manually verified that removing

mockito/src/main/java/org/mockito/internal/junit/ExceptionFactory.java

Lines 22 to 31 in 067ff24

	try {
	Class.forName("org.opentest4j.AssertionFailedError");
	theFactory = org.mockito.exceptions.verification.opentest4j.ArgumentsAreDifferent::new;
	} catch (ClassNotFoundException onlyIfOpenTestIsNotAvailable) {
	try {
	Class.forName("junit.framework.ComparisonFailure");
	theFactory = org.mockito.exceptions.verification.junit.ArgumentsAreDifferent::new;
	} catch (ClassNotFoundException onlyIfJUnitIsNotAvailable) {
	}
	}

and running BasicVerificationTest would reproduce the issue and that the fix is making the test pass as expected.

[mockitoguy]

Should we get rid of removeFirstLine? Otherwise we might be losing first line of the message.

[TimvdLippe]

Are all of our implementations are doing this:

mockito/src/main/java/org/mockito/exceptions/verification/opentest4j/ArgumentsAreDifferent.java

Line 38 in 067ff24

return removeFirstLine(super.toString());

and

mockito/src/main/java/org/mockito/exceptions/verification/junit/ArgumentsAreDifferent.java

Line 38 in 067ff24

return removeFirstLine(super.toString());

I am not sure what the effect of the removal is. Can we separate that change out, to unblock non-opentest4j users and figure out what the impact of removing removeFirstLine will be?

[mockitoguy]

Ok, let's move on. If all tests pass with your change, we should be good to go.