Replace Prelude with RIO

I believe RIO stands for: "ReaderT <something-something> IO", which is a nod to
the top-level application data type:

```haskell
-- This is a simplification
newtype RIO env a = RIO { runRIO :: ReaderT env a () }
```

I read about RIO from an FP-Complete blog post a few months ago, and now I'm
excited to try it out for a real project. Bon voyage!

1 files changed, 2 insertions, 1 deletions

diff --git a/website/sandbox/learnpianochords/src/server/TestUtils.hs b/website/sandbox/learnpianochords/src/server/TestUtils.hs
index e62950369e65..24054bf47afd 100644
--- a/website/sandbox/learnpianochords/src/server/TestUtils.hs
+++ b/website/sandbox/learnpianochords/src/server/TestUtils.hs
@@ -1,6 +1,7 @@
 --------------------------------------------------------------------------------
 module TestUtils where
 --------------------------------------------------------------------------------
+import RIO
 import Web.JWT
 import Data.String.Conversions (cs)
 --------------------------------------------------------------------------------
@@ -9,7 +10,7 @@ unsafeStringOrURI :: String -> StringOrURI
 unsafeStringOrURI x =
   case stringOrURI (cs x) of
     Nothing -> error $ "Failed to convert to StringOrURI: " ++ x
-    Just x  -> x
+    Just res -> res
 
 unsafeJust :: Maybe a -> a
 unsafeJust Nothing = error "Attempted to force a Nothing to be a something"