Handle SystemError in JDBCBackend.get()

Occurs only with Python 3.12 and JPype 1.5.0.

ixmp/backend/jdbc.py

@@ -52,7 +52,6 @@
     "at.ac.iiasa.ixmp.objects.Scenario",
     "at.ac.iiasa.ixmp.Platform",
     "java.lang.Double",
-    "java.lang.Exception",
     "java.lang.Integer",
     "java.lang.NoClassDefFoundError",
     "java.lang.IllegalArgumentException",
@@ -147,7 +146,7 @@ def _handle_jexception():
     """Context manager form of :func:`_raise_jexception`."""
     try:
         yield
-    except java.Exception as e:
+    except jpype.JException as e:
         _raise_jexception(e)
 
 
@@ -708,10 +707,18 @@ def get(self, ts):
         # either getTimeSeries or getScenario
         method = getattr(self.jobj, "get" + ts.__class__.__name__)
 
-        # Re-raise as a ValueError for bad model or scenario name, or other
-        with _handle_jexception():
+        # Re-raise as a ValueError for bad model or scenario name, or other with
+        # with _handle_jexception():
+        try:
             # Either the 2- or 3- argument form, depending on args
             jobj = method(*args)
+        except SystemError:
+            # JPype 1.5.0 with Python 3.12: "<built-in method __subclasscheck__ of
+            # _jpype._JClass object at …> returned a result with an exception set"
+            # At least transmute to a ValueError
+            raise ValueError("model, scenario, or version not found")
+        except BaseException as e:
+            _raise_jexception(e)
 
         self._index_and_set_attrs(jobj, ts)
 
@@ -728,7 +735,7 @@ def check_out(self, ts, timeseries_only):
     def commit(self, ts, comment):
         try:
             self.jindex[ts].commit(comment)
-        except java.Exception as e:
+        except jpype.JException as e:
             arg = e.args[0]
             if isinstance(arg, str) and "this Scenario is not checked out" in arg:
                 raise RuntimeError(arg)