Webapp stuck with "Key duplication when adding: httpModules"

Hi,

some fixes that should improve my situation with "Key duplication when adding: httpModules" problem

Probably want to use the builtin string.format here, and also format the message a bit better.  Personally, I'd prefer to see the second error line in with the first, then simply output the exception, (then possibly the stack trace)  it maybe a developer error, but no reason it can't look nice.