python.pkgs.pyasn1-modules: fix python2 tests (#60618)

Broken by the update in e03d55130f.

pkgs/development/python-modules/pyasn1-modules/default.nix

@@ -1,4 +1,10 @@
-{ stdenv, buildPythonPackage, fetchPypi, pyasn1, isPyPy }:
+{ stdenv
+, buildPythonPackage
+, fetchPypi
+, pyasn1
+, isPyPy
+, pytest
+}:
 
 buildPythonPackage rec {
   pname = "pyasn1-modules";
@@ -11,6 +17,16 @@ buildPythonPackage rec {
 
   propagatedBuildInputs = [ pyasn1 ];
 
+  checkInputs = [
+    pytest
+  ];
+
+  # running tests through setup.py fails only for python2 for some reason:
+  # AttributeError: 'module' object has no attribute 'suitetests'
+  checkPhase = ''
+    py.test
+  '';
+
   meta = with stdenv.lib; {
     description = "A collection of ASN.1-based protocols modules";
     homepage = https://pypi.python.org/pypi/pyasn1-modules;