Fix test failures when Python is compiled without thread support.
diff --git a/Lib/trace.py b/Lib/trace.py
index 6e15e8b..38a13e2 100644
--- a/Lib/trace.py
+++ b/Lib/trace.py
@@ -502,15 +502,7 @@
     def run(self, cmd):
         import __main__
         dict = __main__.__dict__
-        if not self.donothing:
-            threading.settrace(self.globaltrace)
-            sys.settrace(self.globaltrace)
-        try:
-            exec cmd in dict, dict
-        finally:
-            if not self.donothing:
-                sys.settrace(None)
-                threading.settrace(None)
+        self.runctx(cmd, dict, dict)
 
     def runctx(self, cmd, globals=None, locals=None):
         if globals is None: globals = {}