fix possible sys.path bug

--HG--
branch : pmacs2

mode/python.py

@@ -209,6 +209,7 @@ class PythonCheckSyntax(Method):
     '''Check the syntax of the current python file'''
     def _execute(self, w, **vargs):
         pythonlib = w.application.config.get('python.lib')
+        old_path = sys.path
         if pythonlib:
             sys.path.insert(0, pythonlib)
         source = w.buffer.make_string()
@@ -217,9 +218,10 @@ class PythonCheckSyntax(Method):
             w.set_error("Syntax OK")
         except Exception, e:
             output = traceback.format_exc()
-            w.application.data_buffer("*PythonSyntax*", output, switch_to=True,
+            w.application.data_buffer("*PythonSyntax*", output,
+                                      switch_to=True,
                                       modename='error')
-        del sys.path[0]
+        sys.path = old_path
 
 class PythonDictCleanup(Method):
     '''Align assignment blocks and literal dictionaries'''