Handle __del__ more gracefully

exasol/driver/websocket/_connection.py

@@ -150,4 +150,16 @@ def cursor(self):
         return DefaultCursor(self)
 
     def __del__(self):
-        self.close()
+        if self._connection is None:
+            return
+
+        # Currently, the only way to handle this gracefully is to invoke the`__del__`
+        # method of the underlying connection rather than calling an explicit `close`.
+        #
+        # For more details, see also:
+        # * https://github.com/exasol/sqlalchemy-exasol/issues/390
+        # * https://github.com/exasol/pyexasol/issues/108
+        #
+        # If the above tickets are resolved, it should be safe to switch back to using
+        # `close` instead of `__del__`.
+        self._connection.__del__()

test/integration/regression/test_regression_bug390.py

@@ -10,7 +10,7 @@ def test_connection_with_block_cleans_up_properly(pytester, itde):
     pytester.makepyfile(
         # fmt: off
         cleandoc(
-        f"""
+            f"""
         from sqlalchemy import create_engine
         
         def test():