Fiexed #3055 -- Validate that models target of a GenericRelation have a GenericForeignKey field.

Thanks jason for diagnosing the problem and Marcos Moyano for the patch.

git-svn-id: http://code.djangoproject.com/svn/django/trunk@14563 bcc190cf-cafb-0310-a4f2-bffc1f526a37

django/core/management/validation.py

@@ -1,7 +1,14 @@
 import sys
+
+from django.contrib.contenttypes.generic import GenericForeignKey, GenericRelation
 from django.core.management.color import color_style
 from django.utils.itercompat import is_iterable
 
+try:
+    any
+except NameError:
+    from django.utils.itercompat import any
+
 class ModelErrorCollection:
     def __init__(self, outfile=sys.stdout):
         self.errors = []
@@ -224,6 +231,12 @@ def get_validation_errors(outfile, app=None):
                 e.add(opts, "'%s' specifies an m2m relation through model %s, "
                     "which has not been installed" % (f.name, f.rel.through)
                 )
+            elif isinstance(f, GenericRelation):
+                if not any([isinstance(vfield, GenericForeignKey) for vfield in f.rel.to._meta.virtual_fields]):
+                    e.add(opts, "Model '%s' must have a GenericForeignKey in "
+                        "order to create a GenericRelation that points to it."
+                        % f.rel.to.__name__
+                    )
 
             rel_opts = f.rel.to._meta
             rel_name = RelatedObject(f.rel.to, cls, f).get_accessor_name()