Added brief comment.
diff --git a/PCbuild/pytest.bat b/PCbuild/pytest.bat
index 34c32e7..840b44b 100644
--- a/PCbuild/pytest.bat
+++ b/PCbuild/pytest.bat
@@ -1,4 +1,3 @@
+@rem Used by the buildbot "test" step.
 cd PCbuild
 call rt.bat -d -uall -rw
-
-