Mk `test_no_runtime()` not require `pytest-trio`

tests/test_local.py

@@ -10,18 +10,22 @@ import tractor
 from tractor._testing import tractor_test
 
 
-@pytest.mark.trio
-async def test_no_runtime():
-    """A registrar must be established before any nurseries
+def test_no_runtime():
+    '''
+    A registrar must be established before any nurseries
     can be created.
 
     (In other words ``tractor.open_root_actor()`` must be
     engaged at some point?)
-    """
-    with pytest.raises(RuntimeError) :
+
+    '''
+    async def main():
         async with tractor.find_actor('doggy'):
             pass
 
+    with pytest.raises(tractor._exceptions.NoRuntime) :
+        trio.run(main)
+
 
 @tractor_test
 async def test_self_is_registered(reg_addr):