# HG changeset patch
# Parent  57f3514564f62b93847d3867c3a4ff41a082cc92
Issue #27348: Restore “Exception: None” formatting in traceback module

This fixes a regression caused by revision 73afda5a4e4c. Also reverts the
decimal test workaround added in revision 5f3dd0a2b1ab.

Remove test_without_exception(). According to revision ecaafc32c500, this was
added in Python 2 so that print_exc() would output “None” when called with no
exception set. However print_exc() never worked like this in Python 3, and
the use case is not documented.

Restore TracebackCases class name (instead of SyntaxTracebackCases), because
the class also tests other exceptions.

diff -r 57f3514564f6 Lib/_pydecimal.py
--- a/Lib/_pydecimal.py	Tue Jun 28 10:12:22 2016 -0700
+++ b/Lib/_pydecimal.py	Wed Jun 29 08:44:17 2016 +0000
@@ -4157,7 +4157,7 @@
         >>> context.create_decimal_from_float(3.1415926535897932)
         Traceback (most recent call last):
             ...
-        decimal.Inexact
+        decimal.Inexact: None
 
         """
         d = Decimal.from_float(f)       # An exact conversion
diff -r 57f3514564f6 Lib/test/test_traceback.py
--- a/Lib/test/test_traceback.py	Tue Jun 28 10:12:22 2016 -0700
+++ b/Lib/test/test_traceback.py	Wed Jun 29 08:44:17 2016 +0000
@@ -19,7 +19,7 @@
 test_tb = namedtuple('tb', ['tb_frame', 'tb_lineno', 'tb_next'])
 
 
-class SyntaxTracebackCases(unittest.TestCase):
+class TracebackCases(unittest.TestCase):
     # For now, a very minimal set of tests.  I want to be sure that
     # formatting of SyntaxErrors works based on changes for 2.1.
 
@@ -106,10 +106,6 @@
             str_name = '.'.join([X.__module__, X.__qualname__])
         self.assertEqual(err[0], "%s: %s\n" % (str_name, str_value))
 
-    def test_without_exception(self):
-        err = traceback.format_exception_only(None, None)
-        self.assertEqual(err, ['None\n'])
-
     def test_encoded_file(self):
         # Test that tracebacks are correctly printed for encoded source files:
         # - correct line number (Issue2384)
@@ -455,6 +451,17 @@
         msg = self.get_report(e).splitlines()
         self.assertEqual(msg[-2], '              ^')
 
+    def test_message_none(self):
+        # A message that looks like "None" should not be treated specially
+        err = self.get_report(Exception(None))
+        self.assertIn('Exception: None\n', err)
+        err = self.get_report(Exception('None'))
+        self.assertIn('Exception: None\n', err)
+        err = self.get_report(Exception())
+        self.assertIn('Exception\n', err)
+        err = self.get_report(Exception(''))
+        self.assertIn('Exception\n', err)
+
 
 class PyExcReportingTests(BaseExceptionReportingTests, unittest.TestCase):
     #
diff -r 57f3514564f6 Lib/traceback.py
--- a/Lib/traceback.py	Tue Jun 28 10:12:22 2016 -0700
+++ b/Lib/traceback.py	Wed Jun 29 08:44:17 2016 +0000
@@ -140,7 +140,7 @@
 
 def _format_final_exc_line(etype, value):
     valuestr = _some_str(value)
-    if value == 'None' or value is None or not valuestr:
+    if value is None or not valuestr:
         line = "%s\n" % etype
     else:
         line = "%s: %s\n" % (etype, valuestr)
diff -r 57f3514564f6 Misc/NEWS
--- a/Misc/NEWS	Tue Jun 28 10:12:22 2016 -0700
+++ b/Misc/NEWS	Wed Jun 29 08:44:17 2016 +0000
@@ -10,6 +10,10 @@
 Library
 -------
 
+- Issue #27348: In the traceback module, restore the formatting of exception
+  messages like "Exception: None".  This fixes a regression introduced in
+  3.5a2.
+
 - Issue #22115: Added methods trace_add, trace_remove and trace_info in the
   tkinter.Variable class.  They replace old methods trace_variable, trace,
   trace_vdelete and trace_vinfo that use obsolete Tcl commands and might