test(pyston): require command present for options test

The implementation scrapes `-h` output.

Author: scop

test/t/test_pyston.py

@@ -6,7 +6,7 @@ class TestPyston:
     def test_basic(self, completion):
         assert completion
 
-    @pytest.mark.complete("pyston -")
+    @pytest.mark.complete("pyston -", require_cmd=True)
     def test_options(self, completion):
         assert completion