Fixed flake issues

holoviews/util/__init__.py

@@ -120,7 +120,6 @@ def expand_options(cls, options, backend=None):
         """
         current_backend = Store.current_backend
         backend_options = Store.options(backend=backend or current_backend)
-        groups = set(backend_options.groups.keys())
         expanded = {}
         for objspec, options in options.items():
             objtype = objspec.split('.')[0]

tests/core/testdimensioned.py

@@ -1,8 +1,5 @@
-from unittest import SkipTest
-
 from holoviews.core.dimension import Dimensioned
 from holoviews.core.options import Store, Keywords, Options, OptionTree
-from holoviews.element.comparison import ComparisonTestCase
 from ..utils import LoggingComparisonTestCase
 
 class TestObj(Dimensioned):
@@ -61,17 +58,16 @@ def test_apply_options_current_backend_style_invalid_no_match(self):
         with self.assertRaisesRegexp(ValueError, err):
             TestObj([]).options(zxy='A')
 
-    def test_apply_options_explicit_backend_style_invalid(self):
-        err = ("Unexpected option 'style_opt3' for TestObj types "
-               "across all extensions. Similar options for current "
-               "extension \('backend_2'\) are: \['style_opt1', 'style_opt2'\]\.")
+    def test_apply_options_explicit_backend_style_invalid_cross_backend(self):
+        err = ("Unexpected option 'style_opt3' for TestObj types when "
+               "using the 'backend_2' extension. Similar options are: "
+               "\['style_opt1', 'style_opt2'\]\.")
         with self.assertRaisesRegexp(ValueError, err):
             TestObj([]).options(style_opt3='A', backend='backend_2')
 
     def test_apply_options_explicit_backend_style_invalid_no_match(self):
         err = ("Unexpected option 'zxy' for TestObj types when using the "
                "'backend_2' extension. No similar options founds\.")
-
         with self.assertRaisesRegexp(ValueError, err):
             TestObj([]).options(zxy='A', backend='backend_2')