Not enough padding on "Warning: these page should not be the same!"

[SergeyBiryukov]

1. Go to Reading Settings.
2. Assign the same page as Homepage and Posts page.
3. You'll see the two messages: "Settings saved" and "Warning: these page should not be the same!".
4. The first message has enough padding, while the second one does not.

This is caused by generic form table styles:

.form-table td p {
    margin-top: 4px;
    margin-bottom: 0;
}

taking precedence over

div.error p {
    margin: 0.5em 0;
    padding: 2px;
}

Adding a notice class to the message fixes the issue.

Note: This also applies to "Warning: these pages should not be the same as your Privacy Policy page!" directly below.