Fix client_request.post in test

The `post` method of the `client_request` fixture has an argument called
`_data`. There were a few places where we had used an argument of `data`
instead by mistake.

tests/app/main/views/test_add_service.py

@@ -294,7 +294,7 @@ def test_should_return_form_errors_when_service_name_is_empty(
 ):
     page = client_request.post(
         'main.add_service',
-        data={},
+        _data={},
         _expected_status=200,
     )
     assert 'Cannot be empty' in page.text
@@ -306,10 +306,12 @@ def test_add_service_fails_if_service_name_has_less_than_2_alphanumeric_characte
 ):
     page = client_request.post(
         'main.add_service',
-        data={"name": "."},
+        _data={"name": "."},
         _expected_status=200,
     )
-    assert page.find("span", {"class": "govuk-error-message"})
+
+    error_message = page.find("span", {"class": "govuk-error-message"}).text
+    assert 'Must include at least two alphanumeric characters' in error_message
 
 
 def test_should_return_form_errors_with_duplicate_service_name_regardless_of_case(

tests/app/main/views/test_service_settings.py

@@ -3480,7 +3480,7 @@ def test_should_send_branding_and_organisations_to_preview(
     client_request.login(platform_admin_user)
     client_request.post(
         endpoint,
-        data={
+        _data={
             'branding_type': 'org',
             'branding_style': '1'
         },

tests/app/main/views/test_user_profile.py

@@ -94,7 +94,7 @@ def test_should_render_change_email_continue_after_authenticate_email(
         session['new-email'] = 'new_notify@notify.gov.uk'
     page = client_request.post(
         'main.user_profile_email_authenticate',
-        data={'password': '12345'},
+        _data={'password': '12345'},
         _expected_status=200,
     )
     assert 'Click the link in the email to confirm the change to your email address.' in page.text