Bug in `databricks.sql.exc.Error` base class

在 connector 中搜索 databricks.sql.exc.Error 类，并检查其 str 和 message_with_context 方法。复现一个没有消息的 Error，然后验证字符串转换和 message_with_context 不再失败，并且现有的错误行为保持不变。

Problem: When try except catching errors and logging them I occasionally get this TypeError

...
    try:
        with connection.cursor() as cursor:
            cursor.execute(query)
            ...
    except databricks.sql.Error as e:
        logger.debug(f"{str(e)}: failed to execute query {query}")
        ...

__str__ returned non-string (type NoneType)

Explanation:

String representations of a class must be of type string

the message attribute can be None therefore there needs to be a check/cast prior to returning.

Note: message_with_context will also fail when a message is None since you can't use the operand type + for NoneType and a str

class Error(Exception):
    """Base class for DB-API2.0 exceptions.
    `message`: An optional user-friendly error message. It should be short, actionable and stable
    `context`: Optional extra context about the error. MUST be JSON serializable
    """

    def __init__(self, message=None, context=None, *args, **kwargs):
        super().__init__(message, *args, **kwargs)
        self.message = message
        self.context = context or {}

    def __str__(self):
        return self.message

    def message_with_context(self):
        return self.message + ": " + json.dumps(self.context, default=str)