fix: Check if connection initialized when deleting Connection

The session is cleaned up when deleting a connection. But, if the
connection was not fully initialized (e.g. due to a connection error)
then no session will be set.

This will cause __del__ to fail and warnings to be printed to stderr.

We can avoid this by checking if session is set and short-circuiting
before checking if the session is open.

Signed-off-by: Tomás Farías <tomas@tomasfarias.dev>

Author: tomasfarias

src/databricks/sql/client.py

@@ -434,7 +434,8 @@ def __exit__(self, exc_type, exc_value, traceback):
         self.close()
 
     def __del__(self):
-        if self.open:
+        initialized = hasattr(self, "session")
+        if initialized and self.open:
             logger.debug(
                 "Closing unclosed connection for session "
                 "{}".format(self.get_session_id_hex())