Issue #27348: Merge exception formatting fix from 3.5 into 3.6

3 files changed, 14 insertions, 7 deletions

diff --git a/Lib/_pydecimal.py b/Lib/_pydecimal.py
index 6318a49..0b40928 100644
--- a/Lib/_pydecimal.py
+++ b/Lib/_pydecimal.py
@@ -4156,7 +4156,7 @@ class Context(object):
         >>> 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 --git a/Lib/test/test_traceback.py b/Lib/test/test_traceback.py
index ac067bf..f2dc650 100644
--- a/Lib/test/test_traceback.py
+++ b/Lib/test/test_traceback.py
@@ -19,7 +19,7 @@ test_frame = namedtuple('frame', ['f_code', 'f_globals', 'f_locals'])
 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 @@ class SyntaxTracebackCases(unittest.TestCase):
             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)
@@ -587,6 +583,17 @@ class BaseExceptionReportingTests:
         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 --git a/Lib/traceback.py b/Lib/traceback.py
index a1cb5fb..09bda71 100644
--- a/Lib/traceback.py
+++ b/Lib/traceback.py
@@ -140,7 +140,7 @@ def format_exception_only(etype, value):
 
 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)