# HG changeset patch
# User cmlenz
# Date 1175707088 0
# Node ID 7884617bc94143f136b53f5a3ba051a76c8bca11
# Parent  9f11c745fac9bf4edb9be6930396918ce70e2b6c
Add stricter error handling to upgrade notes.

diff --git a/UPGRADE.txt b/UPGRADE.txt
--- a/UPGRADE.txt
+++ b/UPGRADE.txt
@@ -10,6 +10,16 @@
 leftover traces of the `template.py` file on the installation path.
 This is not necessary when Genshi was installed as a Python egg.
 
+Handling of errors in template expressions is now more strict. In
+particular, it is no longer possible to reference an undefined
+variable without an exception being raised. The previous error
+handling let expressions get away with minor typos, which would
+result in subtle bugs that were hard to find. The functions
+`defined()` and `value_of()` are now available in all template
+code; they can be used to test whether a specific variable is
+defined at the top-level scope. Please refer to the template
+language documentation for details.
+
 Results of evaluating template expressions are no longer implicitly
 called if they are callable. If you have been using that feature, you
 will need to add the parenthesis to actually call the function.