SVN: zope.testing/branches/3.5/src/zope/testing/testrunner.py Provide better diagnostics when layer_from_name() fails.

Log message for revision 89132:
  Provide better diagnostics when layer_from_name() fails.
  
  Backported r89123 from trunk.
  
  

Changed:
  U   zope.testing/branches/3.5/src/zope/testing/testrunner.py

-=-
Modified: zope.testing/branches/3.5/src/zope/testing/testrunner.py
===================================================================
--- zope.testing/branches/3.5/src/zope/testing/testrunner.py	2008-08-01 12:28:59 UTC (rev 89131)
+++ zope.testing/branches/3.5/src/zope/testing/testrunner.py	2008-08-01 12:30:25 UTC (rev 89132)
@@ -1564,7 +1564,16 @@
         return _layer_name_cache[layer_name]
     layer_names = layer_name.split('.')
     layer_module, module_layer_name = layer_names[:-1], layer_names[-1]
-    return getattr(import_name('.'.join(layer_module)), module_layer_name)
+    module_name = '.'.join(layer_module)
+    module = import_name(module_name)
+    try:
+        return getattr(module, module_layer_name)
+    except AttributeError, e:
+        # the default error is very uninformative:
+        #   AttributeError: 'module' object has no attribute 'DemoLayer'
+        # it doesn't say *which* module
+        raise AttributeError('module %r has no attribute %r'
+                             % (module_name, module_layer_name))
 
 def order_by_bases(layers):
     """Order the layers from least to most specific (bottom to top)