Get a list of sitesettings files
    
    settings.py can be prefixed with a subdomain and underscore so with example.com site:
    sitesettings/settings.py would be the example.com settings file and
    sitesettings/admin_settings.py would be the admin.example.com settings file

def _sitesettings_files():
    """
    Get a list of sitesettings files
    
    settings.py can be prefixed with a subdomain and underscore so with example.com site:
    sitesettings/settings.py would be the example.com settings file and
    sitesettings/admin_settings.py would be the admin.example.com settings file
    """
    settings_files = []
    sitesettings_path = os.path.join(env.project_package_name,'sitesettings')
    if os.path.exists(sitesettings_path):
        sitesettings = os.listdir(sitesettings_path)
        for file in sitesettings:
            if file == 'settings.py':
                settings_files.append(file)
            elif len(file)>12 and file[-12:]=='_settings.py': #prefixed settings
                settings_files.append(file)
    return settings_files