Added link to error message displayed when TPA only user login from FPA login page

Added link to error message displayed when TPA only user login from FPA login page.
ENT-2535

Fixed pep8 quality violation

skip unit test if context is not LMS

openedx/core/djangoapps/user_authn/views/login.py

@@ -16,6 +16,7 @@ from django.contrib.auth import login as django_login
 from django.contrib.auth.decorators import login_required
 from django.contrib.auth.models import User
 from django.http import HttpRequest, HttpResponse
+from django.urls import reverse
 from django.utils.decorators import method_decorator
 from django.utils.translation import ugettext as _
 from django.views.decorators.csrf import csrf_exempt, csrf_protect, ensure_csrf_cookie
@@ -292,11 +293,19 @@ def _check_user_auth_flow(site, user):
 
         # If user belongs to allowed domain and not whitelisted then user must login through allowed domain SSO
         if user_domain == allowed_domain and not AllowedAuthUser.objects.filter(site=site, email=user.email).exists():
-            msg = _(
-                u'As an {allowed_domain} user, You must login with your {allowed_domain} {provider} account.'
-            ).format(
+            msg = Text(_(
+                u'As {allowed_domain} user, You must login with your {allowed_domain} '
+                u'{link_start}{provider} account{link_end}.'
+            )).format(
                 allowed_domain=allowed_domain,
-                provider=site.configuration.get_value('THIRD_PARTY_AUTH_ONLY_PROVIDER')
+                link_start=HTML("<a href='{tpa_provider_link}'>").format(
+                    tpa_provider_link='{dashboard_url}?tpa_hint={tpa_hint}'.format(
+                        dashboard_url=reverse('dashboard'),
+                        tpa_hint=site.configuration.get_value('THIRD_PARTY_AUTH_HINT'),
+                    )
+                ),
+                provider=site.configuration.get_value('THIRD_PARTY_AUTH_ONLY_PROVIDER'),
+                link_end=HTML("</a>")
             )
             raise AuthFailedError(msg)
 

openedx/core/djangoapps/user_authn/views/tests/test_login.py

@@ -616,6 +616,7 @@ class LoginTest(SiteMixin, CacheIsolationTestCase):
         },
     )
     @ddt.unpack
+    @skip_unless_lms
     def test_login_for_user_auth_flow(
         self,
         switch_enabled,
@@ -629,6 +630,7 @@ class LoginTest(SiteMixin, CacheIsolationTestCase):
         Verify that `login._check_user_auth_flow` works as expected.
         """
         provider = 'Google'
+        provider_tpa_hint = 'saml-test'
         username = 'batman'
         user_email = '{username}@{domain}'.format(username=username, domain=user_domain)
         user = self._create_user(username, user_email)
@@ -636,6 +638,7 @@ class LoginTest(SiteMixin, CacheIsolationTestCase):
             'SITE_NAME': allowed_domain,
             'THIRD_PARTY_AUTH_ONLY_DOMAIN': allowed_domain,
             'THIRD_PARTY_AUTH_ONLY_PROVIDER': provider,
+            'THIRD_PARTY_AUTH_HINT': provider_tpa_hint,
         }
 
         with ENABLE_LOGIN_USING_THIRDPARTY_AUTH_ONLY.override(switch_enabled):
@@ -647,10 +650,14 @@ class LoginTest(SiteMixin, CacheIsolationTestCase):
                 else:
                     AllowedAuthUser.objects.filter(site=site, email=user.email).delete()
 
-                value = None if success else u'As an {0} user, You must login with your {0} {1} account.'.format(
-                    allowed_domain,
-                    provider
-                )
+                if success:
+                    value = None
+                else:
+                    value = u'As {0} user, You must login with your {0} <a href=\'{1}\'>{2} account</a>.'.format(
+                        allowed_domain,
+                        '{}?tpa_hint={}'.format(reverse("dashboard"), provider_tpa_hint),
+                        provider,
+                    )
                 response, __ = self._login_response(user.email, self.password)
                 self._assert_response(
                     response,