Changes in error conditions for multi keyrings

Author: mmegs-amzn

src/aws_encryption_sdk/keyring/multi_keyring.py

@@ -47,8 +47,8 @@ def on_encrypt(self, encryption_materials):
         :rtype: aws_encryption_sdk.materials_managers.EncryptionMaterials
         :raises EncryptKeyError: if unable to encrypt data key.
         """
-        # Check if generator keyring is provided
-        if not self.generator:
+        # Check if generator keyring is not provided and data key is not generated
+        if not self.generator and not encryption_materials.data_encryption_key:
             raise EncryptKeyError("Generator keyring not provided.")
 
         # Check if generator keyring is provided and data key is generated