Improve diagnostic value of expectation failure message for an exit test

Author: grynspan

Sources/Testing/ExitTests/ExitTest.swift

@@ -525,11 +525,11 @@ func callExitTest(
   }
 
   // Plumb the exit test's result through the general expectation machinery.
+  let expression = __Expression(String(describingForTest: expectedExitCondition))
   return __checkValue(
     expectedExitCondition.isApproximatelyEqual(to: result.exitStatus),
     expression: expression,
     expressionWithCapturedRuntimeValues: expression.capturingRuntimeValues(result.exitStatus),
-    mismatchedExitConditionDescription: String(describingForTest: expectedExitCondition),
     comments: comments(),
     isRequired: isRequired,
     sourceLocation: sourceLocation