From cdac302af362f275f31c13e143f78ec682ef7b68 Mon Sep 17 00:00:00 2001
From: Serhiy Storchaka <storchaka@gmail.com>
Date: Sun, 24 Nov 2013 18:15:37 +0200
Subject: [PATCH] Issue #19545: Avoid chained exceptions while passing stray %
 to time.strptime().  Initial patch by Claudiu Popa.

---
 Lib/_strptime.py          | 2 +-
 Lib/test/test_strptime.py | 4 ++++
 Lib/test/test_time.py     | 4 ++++
 Misc/NEWS                 | 3 +++
 4 files changed, 12 insertions(+), 1 deletion(-)

diff --git a/Lib/_strptime.py b/Lib/_strptime.py
index 264d4fa2ed4..9058a698615 100644
--- a/Lib/_strptime.py
+++ b/Lib/_strptime.py
@@ -329,7 +329,7 @@ def _strptime(data_string, format="%a %b %d %H:%M:%S %Y"):
                                     (bad_directive, format)) from None
             # IndexError only occurs when the format string is "%"
             except IndexError:
-                raise ValueError("stray %% in format '%s'" % format)
+                raise ValueError("stray %% in format '%s'" % format) from None
             _regex_cache[format] = format_regex
     found = format_regex.match(data_string)
     if not found:
diff --git a/Lib/test/test_strptime.py b/Lib/test/test_strptime.py
index 68e6a676363..d5bc39d0dd3 100644
--- a/Lib/test/test_strptime.py
+++ b/Lib/test/test_strptime.py
@@ -223,6 +223,10 @@ class StrptimeTests(unittest.TestCase):
         with self.assertRaises(ValueError) as e:
             _strptime._strptime_time('', '%D')
         self.assertIs(e.exception.__suppress_context__, True)
+        # additional check for IndexError branch (issue #19545)
+        with self.assertRaises(ValueError) as e:
+            _strptime._strptime_time('19', '%Y %')
+        self.assertIs(e.exception.__suppress_context__, True)
 
     def test_unconverteddata(self):
         # Check ValueError is raised when there is unconverted data
diff --git a/Lib/test/test_time.py b/Lib/test/test_time.py
index faf9779a473..d8d6029ea5a 100644
--- a/Lib/test/test_time.py
+++ b/Lib/test/test_time.py
@@ -198,6 +198,10 @@ class TimeTestCase(unittest.TestCase):
         with self.assertRaises(ValueError) as e:
             time.strptime('', '%D')
         self.assertIs(e.exception.__suppress_context__, True)
+        # additional check for IndexError branch (issue #19545)
+        with self.assertRaises(ValueError) as e:
+            time.strptime('19', '%Y %')
+        self.assertIs(e.exception.__suppress_context__, True)
 
     def test_asctime(self):
         time.asctime(time.gmtime(self.t))
diff --git a/Misc/NEWS b/Misc/NEWS
index 2a8057ad801..fd53f6259ea 100644
--- a/Misc/NEWS
+++ b/Misc/NEWS
@@ -13,6 +13,9 @@ Core and Builtins
 Library
 -------
 
+- Issue #19545: Avoid chained exceptions while passing stray % to
+  time.strptime().  Initial patch by Claudiu Popa.
+
 - Issue #19633: Fixed writing not compressed 16- and 32-bit wave files on
   big-endian platforms.