python3Packages.ptpython: fix build, add missing black dep

pkgs/development/python-modules/ptpython/default.nix

@@ -1,5 +1,13 @@
-{ lib, buildPythonPackage, pythonOlder, fetchPypi, prompt_toolkit, appdirs, docopt, jedi
-, pygments, importlib-metadata, isPy3k }:
+{ lib, buildPythonPackage, pythonOlder, fetchPypi
+, appdirs
+, black
+, docopt
+, importlib-metadata
+, isPy3k
+, jedi
+, prompt_toolkit
+, pygments
+}:
 
 buildPythonPackage rec {
   pname = "ptpython";
@@ -11,8 +19,14 @@ buildPythonPackage rec {
     sha256 = "4b0f6e381a8251ec8d6aa94fe12f3400bf6edf789f89c8a6099f8a91d4a5d2e1";
   };
 
-  propagatedBuildInputs = [ appdirs prompt_toolkit docopt jedi pygments ]
-    ++ lib.optionals (pythonOlder "3.8") [ importlib-metadata ];
+  propagatedBuildInputs = [
+    appdirs
+    black # yes, this is in install_requires
+    docopt
+    jedi
+    prompt_toolkit
+    pygments
+  ] ++ lib.optionals (pythonOlder "3.8") [ importlib-metadata ];
 
   # no tests to run
   doCheck = false;