Python3 try/except handling improvements. Add Walker exception and use

that: fixes erroneous uncompyle success message on parse error.

test/simple_source/exception/01_try_except.py

@@ -5,23 +5,28 @@
 
 try:
     x = 1
-except RuntimeError as e:
-    y = 2
+except:
+    pass
 
-# # Tests:
-# #   trystmt ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
-# #               try_middle COME_FROM
-# #   except_stmt ::= except_cond1 except_suite
-# #   except_suite ::= ...
+# Tests:
+#   trystmt ::= SETUP_EXCEPT suite_stmts_opt POP_BLOCK
+#               try_middle COME_FROM
+#   except_stmt ::= except_cond1 except_suite
+#   except_suite ::= ...
 
-# try:
-#     x = 1
-# except ImportError:
-#     pass
+try:
+    x = 1
+except ImportError:
+    pass
 
-# try:
-#     x = 2
-# except ImportError:
-#     x = 3
-# finally:
-#     x = 4
+try:
+    x = 2
+except ImportError:
+    x = 3
+finally:
+    x = 4
+
+try:
+    x = 1
+except ImportError as e:
+    x = 2

test/simple_source/exception/05_try_except.py

@@ -1,6 +1,13 @@
+def handle(module):
+    try:
+        module = 1
+    except ImportError as exc:
+        module = exc
+    return module
+
 try:
     pass
 except ImportError as exc:
     pass
 finally:
-    del exc
+    y = 1