[3.6] bpo-30978: str.format_map() now passes key lookup exceptions through. (GH-2790) (#2992)

Previously any exception was replaced with a KeyError exception.
(cherry picked from commit 5075416)

2 files changed, 8 insertions, 1 deletions

diff --git a/Lib/test/test_re.py b/Lib/test/test_re.py
index a6cbbd0..e23e5a9 100644
--- a/Lib/test/test_re.py
+++ b/Lib/test/test_re.py
@@ -471,7 +471,7 @@ class ReTests(unittest.TestCase):
             m[(0,)]
         with self.assertRaisesRegex(IndexError, 'no such group'):
             m[(0, 1)]
-        with self.assertRaisesRegex(KeyError, 'a2'):
+        with self.assertRaisesRegex(IndexError, 'no such group'):
             'a1={a2}'.format_map(m)
 
         m = pat.match('ac')
diff --git a/Lib/test/test_unicode.py b/Lib/test/test_unicode.py
index 2844bc5..56ab0ad 100644
--- a/Lib/test/test_unicode.py
+++ b/Lib/test/test_unicode.py
@@ -1279,6 +1279,13 @@ class UnicodeTest(string_tests.CommonTest,
         self.assertRaises(ValueError, '{}'.format_map, 'a')
         self.assertRaises(ValueError, '{a} {}'.format_map, {"a" : 2, "b" : 1})
 
+        class BadMapping:
+            def __getitem__(self, key):
+                return 1/0
+        self.assertRaises(KeyError, '{a}'.format_map, {})
+        self.assertRaises(TypeError, '{a}'.format_map, [])
+        self.assertRaises(ZeroDivisionError, '{a}'.format_map, BadMapping())
+
     def test_format_huge_precision(self):
         format_string = ".{}f".format(sys.maxsize + 1)
         with self.assertRaises(ValueError):