Simplify the code in s3api

At least now you know that the "with" clause isn't modifying
a self.something behind your back.

The affected part was added when migrating from swift3 to s3api.
As a bonus, the patch makes the code slightly more similar to
the original.

Change-Id: Id4bfbaf971e3a08fdf9d0ef8d7373bb36c298682

swift/common/middleware/s3api/acl_handlers.py

@@ -76,40 +76,28 @@ class BaseAclHandler(object):
     """
     BaseAclHandler: Handling ACL for basic requests mapped on ACL_MAP
     """
-    def __init__(self, req, logger):
+    def __init__(self, req, logger, container=None, obj=None, headers=None):
         self.req = req
-        self.container = self.req.container_name
-        self.obj = self.req.object_name
+        self.container = req.container_name if container is None else container
+        self.obj = req.object_name if obj is None else obj
         self.method = req.environ['REQUEST_METHOD']
         self.user_id = self.req.user_id
-        self.headers = self.req.headers
+        self.headers = req.headers if headers is None else headers
         self.logger = logger
 
     @contextmanager
-    def request_with(self, container=None, obj=None, headers=None):
-        try:
-            org_cont = self.container
-            org_obj = self.obj
-            org_headers = self.headers
-
-            self.container = container or org_cont
-            self.obj = obj or org_obj
-            self.headers = headers or org_headers
-            yield
-
-        finally:
-            self.container = org_cont
-            self.obj = org_obj
-            self.headers = org_headers
+    def request_with(self, container, obj, headers):
+        yield type(self)(self.req, self.logger,
+                         container=container, obj=obj, headers=headers)
 
     def handle_acl(self, app, method, container=None, obj=None, headers=None):
         method = method or self.method
 
-        with self.request_with(container, obj, headers):
-            if hasattr(self, method):
-                return getattr(self, method)(app)
+        with self.request_with(container, obj, headers) as ah:
+            if hasattr(ah, method):
+                return getattr(ah, method)(app)
             else:
-                return self._handle_acl(app, method)
+                return ah._handle_acl(app, method)
 
     def _handle_acl(self, app, sw_method, container=None, obj=None,
                     permission=None, headers=None):
@@ -338,16 +326,16 @@ class MultiUploadAclHandler(BaseAclHandler):
     ========== ====== ============= ==========
 
     """
-    def __init__(self, req, logger):
-        super(MultiUploadAclHandler, self).__init__(req, logger)
+    def __init__(self, req, logger, **kwargs):
+        super(MultiUploadAclHandler, self).__init__(req, logger, **kwargs)
         self.acl_checked = False
 
     def handle_acl(self, app, method, container=None, obj=None, headers=None):
         method = method or self.method
-        with self.request_with(container, obj, headers):
+        with self.request_with(container, obj, headers) as ah:
             # MultiUpload stuffs don't need acl check basically.
-            if hasattr(self, method):
-                return getattr(self, method)(app)
+            if hasattr(ah, method):
+                return getattr(ah, method)(app)
             else:
                 pass
 
@@ -360,9 +348,9 @@ class PartAclHandler(MultiUploadAclHandler):
     """
     PartAclHandler: Handler for PartController
     """
-    def __init__(self, req, logger):
+    def __init__(self, req, logger, **kwargs):
         # pylint: disable-msg=E1003
-        super(MultiUploadAclHandler, self).__init__(req, logger)
+        super(MultiUploadAclHandler, self).__init__(req, logger, **kwargs)
 
     def HEAD(self, app):
         if self.container.endswith(MULTIUPLOAD_SUFFIX):