fix p09, __file__ variable should not be quoted

kyan001 · web-flow · commit 5ddf899f57da · 2017-05-05T20:08:46.000+08:00
diff --git a/source/c10/p09_add_directories_to_sys_path.rst b/source/c10/p09_add_directories_to_sys_path.rst
@@ -54,7 +54,7 @@
 
     import sys
     from os.path import abspath, join, dirname
-    sys.path.insert(0, join(abspath(dirname('__file__')), 'src'))
+    sys.path.insert(0, join(abspath(dirname(__file__)), 'src'))
 
 这将src目录添加到path里，和执行插入步骤的代码在同一个目录里。
 
