Improved help for "import" command at the start of a script when "variable not in scope" in error msg

The piece of code that bgamari wrote in #13891 is interesting from the point of view of the error messages.\\

main = do
    putStrLn "forking"
    forkIO $ bracket (putStrLn "forked") (const $ putStrLn "finalize") (const $ putStrLn "hello" >> threadDelay 100000000)
    threadDelay 10000
    putStrLn "done" 

When the imports are not written GHC answers.\\

Prelude> :l testfork
[1 of 1] Compiling Main             ( testfork.hs, interpreted )

testfork.hs:6:5: error:
    Variable not in scope: forkIO :: t0 -> IO a0

testfork.hs:6:14: error:
    Variable not in scope:
      bracket :: IO () -> (b1 -> IO ()) -> (b0 -> IO b2) -> t0

testfork.hs:6:101: error:
    Variable not in scope: threadDelay :: Integer -> IO b2

testfork.hs:7:5: error:
    Variable not in scope: threadDelay :: Integer -> IO a1
Failed, modules loaded: none.
Prelude>

It would be advisable to complete by:\\ Perhaps you intended to import Control.Concurrent for forkIO and threadDelay.\\

Perhaps you intended to import Control.Exception for bracket.\\ I hope you have a way to write it once for all the variables involved.

Trac metadata

Trac field	Value
Version	8.0.2
Type	FeatureRequest
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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