# HG changeset patch
# User Franz Glasner <hg@dom66.de>
# Date 1460063532 -7200
# Node ID 8715e5cc59ac0967a7559466b001866cfcc72147
# Parent  ce2443285000101dbc72c095b11a727551439d2c
Print a warning if a variable cannot be expanded.

This is to simplify debugging.

diff -r ce2443285000 -r 8715e5cc59ac configmix/config.py
--- a/configmix/config.py	Thu Mar 31 19:19:34 2016 +0200
+++ b/configmix/config.py	Thu Apr 07 23:12:12 2016 +0200
@@ -6,6 +6,7 @@
 
 from __future__ import division, absolute_import, print_function
 
+import warnings
 try:
     from collections import OrderedDict as ConfigurationBase
 except ImportError:
@@ -193,7 +194,14 @@
             if end < 0:
                 return s
             varname, filters = self._split_filters(s[start+2:end])
-            varvalue = self._apply_filters(filters, self.getvar_s(varname))
+            try:
+                varvalue = self._apply_filters(filters, self.getvar_s(varname))
+            except KeyError:
+                warnings.warn("Cannot expand variable %r in string "
+                              "%r" % (varname, s, ),
+                              UserWarning,
+                              stacklevel=1)
+                raise
             if varvalue is None:
                 varvalue = u("")
             replaced = u(b"{0}{1}").format(s[:start], varvalue)