Move letter too long banner message over from utils, also refactor

tests/app/main/views/test_send.py

@@ -2779,9 +2779,7 @@ def test_check_messages_does_not_allow_to_send_letter_longer_than_10_pages(
         _test_page_title=False,
     )
 
-    error = page.select('.banner-dangerous')
-
-    assert normalize_spaces(error[0].text) == 'This letter is too long Letters must be 10 pages or less'
+    assert page.select('#letter-too-long')
 
     assert len(page.select('.letter img')) == 10  # if letter longer than 10 pages, only 10 first pages are displayed
     assert not page.select('[type=submit]')
@@ -3151,11 +3149,7 @@ def test_send_one_off_letter_errors_if_letter_longer_than_10_pages(
         _test_page_title=False,
     )
 
-    assert normalize_spaces(page.select('.banner-dangerous')) == normalize_spaces(
-        'This letter is too long '
-        'Letters must be 10 pages or less'
-    )
-
+    assert page.select('#letter-too-long')
     assert len(page.select('.letter img')) == 10
 
     assert not page.select('[type=submit]')

tests/app/main/views/test_templates.py

@@ -543,6 +543,7 @@ def test_view_letter_template_does_not_display_send_button_if_template_over_10_p
     )
 
     assert "Send" not in page.text
+    assert page.select('#letter-too-long')
 
 
 def test_edit_letter_template_postage_page_displays_correctly(

tests/app/main/views/test_uploads.py

@@ -232,8 +232,7 @@ def test_post_upload_letter_with_letter_that_is_too_long(mocker, client_request)
     assert mock_page_count.called
 
     assert page.find('h1').text == 'tests/test_pdf_files/one_page_pdf.pdf'
-    assert page.find("div", {"class": "banner-dangerous bottom-gutter"})
-    assert "This letter is too long" in page.text
+    assert page.select('#letter-too-long')
     assert not page.find('button', {'type': 'submit'})