[test][test_worker] Remove use of Prefix

beat/core/test/test_worker.py

@@ -246,7 +246,7 @@ class TestWorkerBase(unittest.TestCase):
 
     def start_worker(self, name, address=None):
         args = [
-          '--prefix=%s' % ','.join(prefix.paths),
+          '--prefix=%s' % prefix,
           '--cache=%s' % tmp_prefix,
           '--name=%s' % name,
           # '-vv',