Let's say I add a validation on attachment like this `validates_attachment_size :attachment, :less_than => 10.megabytes` and if I upload a file greater than 10 megabytes then I'll get two errors in `record.errors` i.e.

```
#1: <Attachment> size must be less than 10485760 bytes
#2: <Attachment file> size must be less than 10485760 bytes.
```
Note the words inside angular brackets in both messages. One of them is attribute and the other is base_attribute. We are adding errors on both of them. This should not happen.

#### Note:
After this PR, some test cases are breaking because they are checking the presence of both error messages. In my opinion, only one error message should be added. I can fix the breaking test cases but first I want to know that if my PR is worth working on.