Merge pull request #13090 from mesosphere/finally-undefined

Fix undefined variable f in 'finally' clause of verify-flags-underscore

hack/verify-flags-underscore.py

@@ -36,7 +36,7 @@ def is_binary(pathname):
     @author: Trent Mick <TrentM@ActiveState.com>
     @author: Jorge Orpinel <jorge@orpinel.com>"""
     try:
-        f = open(pathname, 'r')
+        with open(pathname, 'r') as f:
             CHUNKSIZE = 1024
             while 1:
                 chunk = f.read(CHUNKSIZE)
@@ -46,8 +46,7 @@ def is_binary(pathname):
                     break # done
     except:
         return True
-    finally:
-        f.close()
+
     return False
 
 def get_all_files(rootdir):