Introduce a new test helper function: tryExecCardanoCLI

  This is meant as a way to assert on *expected failures*! Sadly, `try` or other exception handling mechanisms do not work inside of the `TestT` monad, so I had to extract and lift the error to be able to catch it and assert on it. Yet, I need to assert on failures and thus, failures should not crash the test early but be assertable as a possible execution outcome.

  There's maybe something more clever to do but I only had a day and a half to spend on all this so I'd rather "get it done".

cardano-cli/test/Test/OptParse.hs

@@ -3,6 +3,7 @@ module Test.OptParse
   , checkTextEnvelopeFormat
   , equivalence
   , execCardanoCLI
+  , tryExecCardanoCLI
   , propertyOnce
   , withSnd
   , noteInputFile
@@ -16,7 +17,10 @@ import           Cardano.Api
 
 import           Cardano.CLI.Shelley.Run.Read
 
+import           Control.Monad.Trans.Class (lift)
+import           Control.Monad.Trans.Except (runExceptT)
 import           Control.Monad.IO.Class (MonadIO (..))
+import           Data.Function ((&))
 import           GHC.Stack (CallStack, HasCallStack)
 import qualified Hedgehog as H
 import qualified Hedgehog.Extras.Test.Process as H
@@ -37,6 +41,20 @@ execCardanoCLI
   -- ^ Captured stdout
 execCardanoCLI = GHC.withFrozenCallStack $ H.execFlex "cardano-cli" "CARDANO_CLI"
 
+tryExecCardanoCLI
+  :: [String]
+  -- ^ Arguments to the CLI command
+  -> H.PropertyT IO (Either H.Failure String)
+  -- ^ Captured stdout, or error in case of failures
+tryExecCardanoCLI args =
+  GHC.withFrozenCallStack (H.execFlex "cardano-cli" "CARDANO_CLI") args
+    & H.unPropertyT
+    & H.unTest
+    & runExceptT
+    & lift
+    & H.TestT
+    & H.PropertyT
+
 -- | Checks that the 'tvType' and 'tvDescription' are equivalent between two files.
 checkTextEnvelopeFormat
   :: (MonadTest m, MonadIO m, HasCallStack)