small bug with account to account copy

Change-Id: I7fdf432666f7640082e9839b9dc3d7af94a0715f

swift/common/constraints.py

@@ -388,6 +388,10 @@ def check_account_format(req, account):
     :raise: HTTPPreconditionFailed if account header
             is not well formatted.
     """
+    if not account:
+        raise HTTPPreconditionFailed(
+            request=req,
+            body='Account name cannot be empty')
     if isinstance(account, unicode):
         account = account.encode('utf-8')
     if '/' in account:

test/unit/common/test_constraints.py

@@ -502,6 +502,12 @@ class TestConstraints(unittest.TestCase):
         self.assertRaises(HTTPException,
                           constraints.check_account_format,
                           req, req.headers['X-Copy-From-Account'])
+        req = Request.blank(
+            '/v/a/c/o',
+            headers={'X-Copy-From-Account': ''})
+        self.assertRaises(HTTPException,
+                          constraints.check_account_format,
+                          req, req.headers['X-Copy-From-Account'])
 
 
 class TestConstraintsConfig(unittest.TestCase):