[common][models] Improved declaration_string to ensure a string is returned

beat/web/common/models.py

@@ -41,6 +41,7 @@ from . import storage
 
 from .exceptions import NotUserNorTeam
 from .signals import shared
+from .utils import ensure_string
 
 import os
 import re
@@ -640,7 +641,8 @@ def get_declaration(instance):
 
 
 def get_declaration_string(instance):
-    return storage.get_file_content(instance, 'declaration_file')
+    data = storage.get_file_content(instance, 'declaration_file')
+    return ensure_string(data)
 
 
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