Specify bio message for user

Currently user message is generic. Specifying for
bio field so that it make more sense to user.

PROD-1582

openedx/core/djangoapps/user_api/accounts/tests/test_views.py

@@ -611,10 +611,15 @@ class TestAccountsAPI(CacheIsolationTestCase, UserAPITestCase):
 
         if fails_validation_value:
             error_response = self.send_patch(client, {field: fails_validation_value}, expected_status=400)
+            expected_user_message = u'This value is invalid.'
+            if field == 'bio':
+                expected_user_message = u"The about me field must be at most 300 characters long."
+
             self.assertEqual(
-                u'This value is invalid.',
+                expected_user_message,
                 error_response.data["field_errors"][field]["user_message"]
             )
+
             self.assertEqual(
                 u"Value '{value}' is not valid for field '{field}': {messages}".format(
                     value=fails_validation_value, field=field, messages=[developer_validation_message]

openedx/core/lib/api/view_utils.py

@@ -23,6 +23,7 @@ from rest_framework.views import APIView
 from six import text_type, iteritems
 
 from openedx.core.djangoapps.content.course_overviews.models import CourseOverview
+from openedx.core.djangoapps.user_api.accounts import BIO_MAX_LENGTH
 from openedx.core.lib.api.authentication import BearerAuthenticationAllowInactiveUser
 from openedx.core.lib.api.permissions import IsUserInUrl
 
@@ -154,11 +155,16 @@ def add_serializer_errors(serializer, data, field_errors):
         errors = serializer.errors
         for key, error in iteritems(errors):
             error = clean_errors(error)
+            if key == 'bio':
+                user_message = _(u"The about me field must be at most {} characters long.".format(BIO_MAX_LENGTH))
+            else:
+                user_message = _(u"This value is invalid.")
+
             field_errors[key] = {
                 'developer_message': u"Value '{field_value}' is not valid for field '{field_name}': {error}".format(
                     field_value=data.get(key, ''), field_name=key, error=error
                 ),
-                'user_message': _(u"This value is invalid."),
+                'user_message': user_message,
             }
     return field_errors