python2.pkgs.markdown: keep at 3.1.1 for Python 2

pkgs/development/python-modules/markdown/3_1.nix

@@ -0,0 +1,34 @@
+{ lib
+, buildPythonPackage
+, fetchPypi
+, setuptools
+, nose
+, pyyaml
+, pythonOlder
+, importlib-metadata
+, isPy3k
+}:
+
+buildPythonPackage rec {
+  pname = "Markdown";
+  version = "3.1.1";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "2e50876bcdd74517e7b71f3e7a76102050edec255b3983403f1a63e7c8a41e7a";
+  };
+
+  propagatedBuildInputs = [ 
+    setuptools 
+  ] ++ lib.optionals (pythonOlder "3.8") [
+    importlib-metadata
+  ];
+
+  checkInputs = [ nose pyyaml ];
+
+  meta = {
+    description = "A Python implementation of John Gruber's Markdown with Extension support";
+    homepage = "https://github.com/Python-Markdown/markdown";
+    license = lib.licenses.bsd3;
+  };
+}

pkgs/top-level/python-packages.nix

@@ -4504,7 +4504,10 @@ in {
 
   mapsplotlib = callPackage ../development/python-modules/mapsplotlib { };
 
-  markdown = callPackage ../development/python-modules/markdown { };
+  markdown = if isPy3k then
+    callPackage ../development/python-modules/markdown { }
+  else
+    callPackage ../development/python-modules/markdown/3_1.nix { };
 
   markdownsuperscript = callPackage ../development/python-modules/markdownsuperscript {};