Close internal session when transport is deleted

src/zeep/transports.py

@@ -37,6 +37,7 @@ def __init__(self, cache=None, timeout=300, operation_timeout=None, session=None
         self.operation_timeout = operation_timeout
         self.logger = logging.getLogger(__name__)
 
+        self.__close_session = not session
         self.session = session or requests.Session()
         self.session.mount("file://", FileAdapter())
         self.session.headers["User-Agent"] = "Zeep/%s (www.python-zeep.org)" % (
@@ -154,6 +155,10 @@ def settings(self, timeout=None):
         yield
         self.operation_timeout = old_timeout
 
+    def __del__(self):
+        if self.__close_session:
+            self.session.close()
+
 
 class AsyncTransport(Transport):
     """Asynchronous Transport class using httpx.