Updating validation error message on signup page.

ECOM-1956

common/djangoapps/student/forms.py

@@ -108,7 +108,7 @@ class AccountCreationForm(forms.Form):
         max_length=30,
         error_messages={
             "required": _USERNAME_TOO_SHORT_MSG,
-            "invalid": _("Username should only consist of A-Z and 0-9, with no spaces."),
+            "invalid": _("Usernames must contain only letters, numbers, underscores (_), and hyphens (-)."),
             "min_length": _USERNAME_TOO_SHORT_MSG,
             "max_length": _("Username cannot be more than %(limit_value)s characters long"),
         }

common/djangoapps/student/tests/test_create_account.py

@@ -310,7 +310,7 @@ class TestCreateAccountValidation(TestCase):
 
         # Invalid
         params["username"] = "invalid username"
-        assert_username_error("Username should only consist of A-Z and 0-9, with no spaces.")
+        assert_username_error("Usernames must contain only letters, numbers, underscores (_), and hyphens (-).")
 
     def test_email(self):
         params = dict(self.minimal_params)