Make sure parentheses are escaped when used in the format string.

Closes bug #796149 .  Will be backported.

Lib/_strptime.py

@@ -249,7 +249,7 @@ class TimeRE(dict):
         processed_format = ''
         # The sub() call escapes all characters that might be misconstrued
         # as regex syntax.
-        regex_chars = re_compile(r"([\\.^$*+?{}\[\]|])")
+        regex_chars = re_compile(r"([\\.^$*+?\(\){}\[\]|])")
         format = regex_chars.sub(r"\\\1", format)
         whitespace_replacement = re_compile('\s+')
         format = whitespace_replacement.sub('\s*', format)

Lib/test/test_strptime.py

@@ -333,6 +333,15 @@ class StrptimeTests(unittest.TestCase):
                         "Default values for strptime() are incorrect;"
                         " %s != %s" % (strp_output, defaults))
 
+    def test_escaping(self):
+        # Make sure all characters that have regex significance are escaped.
+        # Parentheses are in a purposeful order; will cause an error of
+        # unbalanced parentheses when the regex is compiled if they are not
+        # escaped.
+        # Test instigated by bug #796149 .
+        need_escaping = ".^$*+?{}\[]|)("
+        self.failUnless(_strptime.strptime(need_escaping, need_escaping))
+
 class Strptime12AMPMTests(unittest.TestCase):
     """Test a _strptime regression in '%I %p' at 12 noon (12 PM)"""