test/assemblers: skip unless we can bind mount

We need to be able to bind-mount in the assembler tests, so skip
all of those if we can't (because we are not root).

test/run/test_assemblers.py

@@ -18,6 +18,7 @@ MEBIBYTE = 1024 * 1024
 
 
 @unittest.skipUnless(test.TestBase.have_test_data(), "no test-data access")
+@unittest.skipUnless(test.TestBase.can_bind_mount(), "root-only")
 class TestAssemblers(test.TestBase):
     @classmethod
     def setUpClass(cls):