Do not allow empty identifiers in PythonIdentifier.issue6

This restores the previous behaviour of validate(); fromUnicode() previously did no validation at all.

2 files changed, 7 insertions, 2 deletions

diff --git a/docs/api/fields.rst b/docs/api/fields.rst
index 1a81b8d..928a632 100644
--- a/docs/api/fields.rst
+++ b/docs/api/fields.rst
@@ -43,7 +43,7 @@
       Validation Error '3foo'
       Validation Error 'foo:'
       Validation Error '\\'
-      ''
+      Validation Error ''
 
 .. autoclass:: GlobalObject
    :members:
diff --git a/src/zope/configuration/fields.py b/src/zope/configuration/fields.py
index add0fe8..b27a236 100644
--- a/src/zope/configuration/fields.py
+++ b/src/zope/configuration/fields.py
@@ -35,9 +35,14 @@ from zope.configuration.interfaces import InvalidToken
 
 class PythonIdentifier(schema_PythonIdentifier):
     """
-    This class is deprecated, prefer `zope.schema.PythonIdentifier`.
+    This class is like `zope.schema.PythonIdentifier`, but does not allow empty strings.
     """
 
+    def _validate(self, value):
+        super(PythonIdentifier, self)._validate(value)
+        if not value:
+            raise ValidationError(value).with_field_and_value(self, value)
+
 
 @implementer(IFromUnicode)
 class GlobalObject(Field):