Issue Summary

Basic authentication for API calls no longer work when SAML/SSO is enabled and the login form has been disabled.

This is reproducible on Data Center: yes

Steps to Reproduce

1. 4.2.27 SSO for Data Center
2. Turn on "Allow basic authentication for REST API calls".
3. Disable the "Show on Login Page" for type "Product Login form" for Username and Password.

Expected Results

Basic authentication can be used for REST API calls.

Actual Results

Attempts to use REST API with Basic Authentication result in errors like:

""message": "Login form has been disabled on this instance.""

Workaround

The only known workaround is to enable "Show on Login Page" for Product Login Form for Username and Password.