Migrate io-tests from bash to pytest

Authored-by: monacoremo <monacoremo>

nix/style.nix

@@ -1,4 +1,5 @@
-{ buildEnv
+{ black
+, buildEnv
 , checkedShellScript
 , git
 , hlint
@@ -19,6 +20,9 @@ let
         # --vimgrep fixes a bug in ag: https://github.com/ggreer/the_silver_searcher/issues/753
         ${silver-searcher}/bin/ag -l --vimgrep -g '\.l?hs$' . "$rootdir" \
           | xargs ${stylish-haskell}/bin/stylish-haskell -i
+
+        # Format Python files
+        ${black}/bin/black "$rootdir" 2> /dev/null
       '';
 
   # Script to check whether any uncommited changes result from postgrest-style