[Haskell-cafe] doctest: Interpreter exited with an error: ExitFailure 127

[informationen]

Hi,

i have upgraded to doctest version 0.4.1.
Now when i try to run the example from the webpage, i get:

doctest: Interpreter exited with an error: ExitFailure 127

What's wrong here and how can i fix it?

Kind regards 

Chris

This is the content of Fib.hs:

module Fib where
  
-- | Compute Fibonacci numbers
--
-- Examples:
--
-- >>> fib 10
-- 55
--
-- >>> fib 5
-- 5
fib 0 = 0
fib 1 = 1
fib n = fib (n - 1) + fib (n - 2)

main = do print $ fib 4