Error when ForEach or other ControlActivity expression evaluates to an unexpected type is not clear

[arjendev]

Whenever a ControlActivities expression is not evaluating to an array (for ForEach, Until etc..), the error is very unclear.

The error shown would be a DataFactoryElementEvaluationError exception with a nested exception that would indicate: TypeError: string indices must be integers, not 'str'. Ideally the exception would be: ForEachExpressionObjectEvaluatedNotToAnArrayError or something more catchy.