Invalid patterns to substitute and safe_substitute would crash since pattern

is not a local variable.  Add a test case.

1 files changed, 4 insertions, 2 deletions

diff --git a/Lib/string.py b/Lib/string.py
index 7371c915a1..e10087eb2a 100644
--- a/Lib/string.py
+++ b/Lib/string.py
@@ -167,7 +167,8 @@ class Template:
                 return self.delimiter
             if mo.group('invalid') is not None:
                 self._invalid(mo)
-            raise ValueError('Unrecognized named group in pattern', pattern)
+            raise ValueError('Unrecognized named group in pattern',
+                             self.pattern)
         return self.pattern.sub(convert, self.template)
 
     def safe_substitute(self, *args, **kws):
@@ -199,7 +200,8 @@ class Template:
                 return self.delimiter
             if mo.group('invalid') is not None:
                 self._invalid(mo)
-            raise ValueError('Unrecognized named group in pattern', pattern)
+            raise ValueError('Unrecognized named group in pattern',
+                             self.pattern)
         return self.pattern.sub(convert, self.template)