pythonPackage.cli-helpers: disable python2 tests

pkgs/development/python-modules/cli-helpers/default.nix

@@ -1,14 +1,11 @@
-{ lib
-, buildPythonPackage
-, fetchPypi
+{ lib, buildPythonPackage, fetchPypi, isPy27
+, backports_csv
 , configobj
-, terminaltables
+, mock
+, pytest
 , tabulate
-, backports_csv
+, terminaltables
 , wcwidth
-, pytest
-, mock
-, isPy27
 }:
 
 buildPythonPackage rec {
@@ -27,6 +24,9 @@ buildPythonPackage rec {
     wcwidth
   ] ++ (lib.optionals isPy27 [ backports_csv ]);
 
+  # namespace collision between backport.csv and backports.configparser
+  doCheck = !isPy27;
+
   checkInputs = [ pytest mock ];
 
   checkPhase = ''