Require a homepage field in pubspecs.

utils/pub/validator/pubspec_field.dart

Index: utils/pub/validator/pubspec_field.dart
diff --git a/utils/pub/validator/pubspec_field.dart b/utils/pub/validator/pubspec_field.dart
index 4c63d9bbec02cbc7e430f283fe3b76c1cb1e9475..e7e8ca733821bbe5c8bda3e1998e6dfa1e7b2125 100644
--- a/utils/pub/validator/pubspec_field.dart
+++ b/utils/pub/validator/pubspec_field.dart
@@ -43,6 +43,11 @@ class PubspecFieldValidator extends Validator {
       errors.add('pubspec.yaml is missing a "homepage" field.');
     }
 
+    var description = pubspec.fields['description'];
+    if (description == null) {
+      errors.add('pubspec.yaml is missing a "description" field.');
+    }
+
     return new Future.immediate(null);
   }
 }