Added check for duplication of email

common/djangoapps/student/forms.py

@@ -243,6 +243,12 @@ class AccountCreationForm(forms.Form):
                 # reject the registration.
                 if not CourseEnrollmentAllowed.objects.filter(email=email).exists():
                     raise ValidationError(_("Unauthorized email address."))
+        if User.objects.filter(email__iexact=email).exists():
+            raise ValidationError(
+                _(
+                    "It looks like {email} belongs to an existing account. Try again with a different email address."
+                ).format(email=email)
+            )
         return email
 
     def clean_year_of_birth(self):

common/djangoapps/student/views.py

@@ -1899,7 +1899,7 @@ def auto_auth(request):
     # the new user object.
     try:
         user, profile, reg = _do_create_account(form)
-    except AccountValidationError:
+    except (AccountValidationError, ValidationError):
         # Attempt to retrieve the existing user.
         user = User.objects.get(username=username)
         user.email = email

common/djangoapps/third_party_auth/tests/specs/base.py

@@ -374,7 +374,7 @@ class IntegrationTest(testutil.TestCase, test.TestCase):
         self.assertEqual(400, response.status_code)
         payload = json.loads(response.content)
         self.assertFalse(payload.get('success'))
-        self.assertIn('already exists', payload.get('value'))
+        self.assertIn('belongs to an existing account', payload.get('value'))
 
     def assert_json_success_response_looks_correct(self, response):
         """Asserts the json response indicates success and redirection."""