Return more helpful error messages when a resource conflict occurs

common/djangoapps/user_api/tests/test_views.py

@@ -832,9 +832,6 @@ class RegistrationViewTest(ApiTestCase):
                 u"required": True,
                 u"label": u"Email",
                 u"placeholder": u"username@domain.com",
-                u"instructions": u"The email address you used to register with {platform_name}".format(
-                    platform_name=settings.PLATFORM_NAME
-                ),
                 u"restrictions": {
                     "min_length": account_api.EMAIL_MIN_LENGTH,
                     "max_length": account_api.EMAIL_MAX_LENGTH
@@ -913,9 +910,6 @@ class RegistrationViewTest(ApiTestCase):
                     u"required": True,
                     u"label": u"Email",
                     u"placeholder": u"username@domain.com",
-                    "instructions": "The email address you used to register with {platform_name}".format(
-                        platform_name=settings.PLATFORM_NAME
-                    ),
                     u"restrictions": {
                         "min_length": account_api.EMAIL_MIN_LENGTH,
                         "max_length": account_api.EMAIL_MAX_LENGTH
@@ -1354,7 +1348,10 @@ class RegistrationViewTest(ApiTestCase):
             "honor_code": "true",
         })
         self.assertEqual(response.status_code, 409)
-        self.assertEqual(response.content, json.dumps(["email"]))
+        self.assertEqual(
+            response.content,
+            "It looks like {} belongs to an existing account.".format(self.EMAIL)
+        )
 
     def test_register_duplicate_username(self):
         # Register the first user
@@ -1376,7 +1373,10 @@ class RegistrationViewTest(ApiTestCase):
             "honor_code": "true",
         })
         self.assertEqual(response.status_code, 409)
-        self.assertEqual(response.content, json.dumps(["username"]))
+        self.assertEqual(
+            response.content,
+            "It looks like {} belongs to an existing account.".format(self.USERNAME)
+        )
 
     def test_register_duplicate_username_and_email(self):
         # Register the first user
@@ -1398,7 +1398,12 @@ class RegistrationViewTest(ApiTestCase):
             "honor_code": "true",
         })
         self.assertEqual(response.status_code, 409)
-        self.assertEqual(response.content, json.dumps(["email", "username"]))
+        self.assertEqual(
+            response.content,
+            "It looks like {} and {} belong to an existing account.".format(
+                self.EMAIL, self.USERNAME
+            )
+        )
 
     def _assert_reg_field(self, extra_fields_setting, expected_field):
         """Retrieve the registration form description from the server and

common/djangoapps/user_api/views.py

@@ -255,16 +255,36 @@ class RegistrationView(APIView):
             HttpResponse: 302 if redirecting to another page.
 
         """
-        # Handle duplicate username/email
-        conflicts = account_api.check_account_exists(
-            username=request.POST.get('username'),
-            email=request.POST.get('email')
-        )
+        email = request.POST.get('email')
+        username = request.POST.get('username')
+
+        # Handle duplicate email/username
+        conflicts = account_api.check_account_exists(email=email, username=username)
         if conflicts:
+            if all(conflict in conflicts for conflict in ['email', 'username']):
+                # Translators: This message is shown to users who attempt to create a new
+                # account using both an email address and a username associated with an
+                # existing account.
+                error_msg = _(
+                    u"It looks like {email_address} and {username} belong to an existing account."
+                ).format(email_address=email, username=username)
+            elif 'email' in conflicts:
+                # Translators: This message is shown to users who attempt to create a new
+                # account using an email address associated with an existing account.
+                error_msg = _(
+                    u"It looks like {email_address} belongs to an existing account."
+                ).format(email_address=email)
+            else:
+                # Translators: This message is shown to users who attempt to create a new
+                # account using a username associated with an existing account.
+                error_msg = _(
+                    u"It looks like {username} belongs to an existing account."
+                ).format(username=username)
+
             return HttpResponse(
                 status=409,
-                content=json.dumps(conflicts),
-                content_type="application/json"
+                content=error_msg,
+                content_type="text/plain"
             )
 
         # For the initial implementation, shim the existing login view
@@ -281,18 +301,11 @@ class RegistrationView(APIView):
         # a field on the registration form meant to hold the user's email address.
         email_placeholder = _(u"username@domain.com")
 
-        # Translators: These instructions appear on the registration form, immediately
-        # below a field meant to hold the user's email address.
-        email_instructions = _(
-            u"The email address you used to register with {platform_name}"
-        ).format(platform_name=settings.PLATFORM_NAME)
-
         form_desc.add_field(
             "email",
             field_type="email",
             label=email_label,
             placeholder=email_placeholder,
-            instructions=email_instructions,
             restrictions={
                 "min_length": account_api.EMAIL_MIN_LENGTH,
                 "max_length": account_api.EMAIL_MAX_LENGTH,