Replaced execfile() with exec(open().read()) in gevent/monkey.py.

gevent/monkey.py

@@ -239,6 +239,7 @@ MONKEY OPTIONS: --verbose %s""" % ', '.join('--[no-]%s' % m for m in modules)
         sys.argv = argv
         __package__ = None
         globals()['__file__'] = sys.argv[0]  # issue #302
-        execfile(sys.argv[0])
+        with open(sys.argv[0]) as f:
+            exec(f.read())
     else:
         print(script_help)