Issue #21855: Fixed the decimal module in unicode disabled build.
diff --git a/Lib/decimal.py b/Lib/decimal.py
index 19cc50f..07c2cec 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -6035,7 +6035,10 @@
         format_dict['decimal_point'] = '.'
 
     # record whether return type should be str or unicode
-    format_dict['unicode'] = isinstance(format_spec, unicode)
+    try:
+        format_dict['unicode'] = isinstance(format_spec, unicode)
+    except NameError:
+        format_dict['unicode'] = False
 
     return format_dict