Fix error when closing session in transport destructor

Fixes #1347

CHANGES

@@ -1,4 +1,8 @@
-4.2.0 (2022-111-03)
+4.2.1 (2022-11-10)
+-------------------
+ - Fix error regarding closing session in async transport (#1347)
+
+4.2.0 (2022-11-03)
 -------------------
  - Drop support for Python 3.6
  - Allow embedding CDATA elements in simple types (#1339)

src/zeep/transports.py

@@ -37,7 +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._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)" % (
@@ -156,7 +156,7 @@ def settings(self, timeout=None):
         self.operation_timeout = old_timeout
 
     def __del__(self):
-        if self.__close_session:
+        if self._close_session:
             self.session.close()
 
 
@@ -181,6 +181,7 @@ def __init__(
         if httpx is None:
             raise RuntimeError("The AsyncTransport is based on the httpx module")
 
+        self._close_session = False
         self.cache = cache
         self.wsdl_client = wsdl_client or httpx.Client(
             verify=verify_ssl,