python2.pkgs: move expressions into python2-modules/ folder

Another step in further separating python2 from python3.

pkgs/development/python2-modules/pytest-runner/default.nix

@@ -0,0 +1,30 @@
+{ lib, buildPythonPackage, fetchPypi, setuptools-scm, pytest }:
+
+buildPythonPackage rec {
+  pname = "pytest-runner";
+  version = "5.2";
+
+  src = fetchPypi {
+    inherit pname version;
+    sha256 = "96c7e73ead7b93e388c5d614770d2bae6526efd997757d3543fe17b557a0942b";
+  };
+
+  nativeBuildInputs = [ setuptools-scm pytest ];
+
+  postPatch = ''
+    rm pytest.ini
+  '';
+
+  checkPhase = ''
+    py.test tests
+  '';
+
+  # Fixture not found
+  doCheck = false;
+
+  meta = with lib; {
+    description = "Invoke py.test as distutils command with dependency resolution";
+    homepage = "https://github.com/pytest-dev/pytest-runner";
+    license = licenses.mit;
+  };
+}