don't override execfile on Python 2

IPython/utils/py3compat.py

@@ -47,6 +47,10 b' if sys.version_info[0] >= 3:'
     
     MethodType = types.MethodType
 
+    def execfile(fname, glob, loc=None):
+        loc = loc if (loc is not None) else glob
+        exec compile(open(fname).read(), fname, 'exec') in glob, loc
+
 else:
     PY3 = False
     
@@ -90,6 +94,6 b' else:'
     def MethodType(func, instance):
         return types.MethodType(func, instance, type(instance))
 
-def execfile(fname, glob, loc=None):
-    loc = loc if (loc is not None) else glob
-    exec compile(open(fname).read(), fname, 'exec') in glob, loc
+    # don't override system execfile on 2.x:
+    execfile = execfile
+