Ignore underscored files when compiling a directory.

sass.py

@@ -149,7 +149,8 @@ def compile_dirname(
     fs_encoding = sys.getfilesystemencoding() or sys.getdefaultencoding()
     for dirpath, _, filenames in os.walk(search_path):
         filenames = [
-            filename for filename in filenames if filename.endswith('.scss')
+            filename for filename in filenames
+            if filename.endswith('.scss') and not filename.startswith('_')
         ]
         for filename in filenames:
             input_filename = os.path.join(dirpath, filename)

sasstests.py

@@ -698,7 +698,6 @@ def test_successful(self):
             # Make sure we don't compile non-scss files
             write_file(os.path.join(input_dir, 'baz.txt'), 'Hello der')
 
-            # the api for this is weird, why does it need source?
             sass.compile(dirname=(input_dir, output_dir))
             assert os.path.exists(output_dir)
             assert os.path.exists(os.path.join(output_dir, 'foo'))
@@ -711,6 +710,17 @@ def test_successful(self):
             self.assertEqual(contentsf1, 'a b {\n  width: 100%; }\n')
             self.assertEqual(contentsf2, 'foo {\n  width: 100%; }\n')
 
+    def test_ignores_underscored_files(self):
+        with tempdir() as tmpdir:
+            input_dir = os.path.join(tmpdir, 'input')
+            output_dir = os.path.join(tmpdir, 'output')
+            os.mkdir(input_dir)
+            write_file(os.path.join(input_dir, 'f1.scss'), '@import "f2";')
+            write_file(os.path.join(input_dir, '_f2.scss'), 'a{color:red}')
+
+            sass.compile(dirname=(input_dir, output_dir))
+            assert not os.path.exists(os.path.join(output_dir, '_f2.css'))
+
     def test_error(self):
         with tempdir() as tmpdir:
             input_dir = os.path.join(tmpdir, 'input')