fix with python2

sass.py

@@ -600,15 +600,8 @@ def _get_file_arg(key):
             'custom_import_extensions must be a list of strings '
             'not {}'.format(type(_custom_exts))
         )
-    custom_import_extensions = []
-    for ext in _custom_exts:
-        if isinstance(ext, text_type):
-            custom_import_extensions.append(ext.encode('utf-8'))
-        else:
-            raise TypeError(
-                'custom_import_extensions must be a list of strings '
-                'not {}'.format(type(ext))
-            )
+    custom_import_extensions = [ext.encode('utf-8') for ext in _custom_exts]
+
     importers = _validate_importers(kwargs.pop('importers', None))
 
     if 'string' in modes:

sasstests.py

@@ -1435,19 +1435,14 @@ def test_import_css(exts, tmpdir):
     assert out == 'body {\n  color: green; }\n'
 
 
-@pytest.mark.parametrize('exts', [
-    ['.css', 3],
-    '.css',
-    [b'.css'],
-])
-def test_import_css_error(exts, tmpdir):
+def test_import_css_error(tmpdir):
     tmpdir.join('other.css').write('body {color: green}')
     main_scss = tmpdir.join('main.scss')
     main_scss.write("@import 'other';")
     with pytest.raises(TypeError):
         sass.compile(
             filename=main_scss.strpath,
-            custom_import_extensions=exts,
+            custom_import_extensions='.css',
         )