include docker error reason in sandbox start failure response

domain/error.py

@@ -23,9 +23,10 @@ class SandboxError(DomainError):
 
 
 class SandboxStartError(SandboxError):
-    def __init__(self, chat_id: str) -> None:
+    def __init__(self, chat_id: str, reason: str = '') -> None:
         super().__init__('sandbox_start_failed')
         self.chat_id = chat_id
+        self.reason = reason
 
 
 class SandboxAlreadyRunningError(SandboxError):