Resolving dependencies...
Downloading Command-0.0.5...
Configuring Command-0.0.5...
Building Command-0.0.5...
Preprocessing library Command-0.0.5...
[1 of 1] Compiling System.Command   ( src/System/Command.hs, dist/build/System/Command.o )

src/System/Command.hs:182:27:
    Could not deduce (Functor m) arising from a use of `void'
    from the context (Monad m)
      bound by the type signature for
                 ->>> :: Monad m => m ExitCode -> m a -> m ()
      at src/System/Command.hs:(176,3)-(179,9)
    Possible fix:
      add (Functor m) to the context of
        the type signature for ->>> :: Monad m => m ExitCode -> m a -> m ()
    In the second argument of `when', namely `(void b)'
    In a stmt of a 'do' block: when (isSuccess a') (void b)
    In the expression:
      do { a' <- a;
           when (isSuccess a') (void b) }
Failed to install Command-0.0.5
cabal: Error: some packages failed to install:
Command-0.0.5 failed during the building phase. The exception was:
ExitFailure 1