          if not auth or auth[0].lower() != b'basic':
              return None
  
          if len(auth) == 1:
              msg = _("Invalid basic header. No credentials provided.")
              raise exceptions.AuthenticationFailed(msg)
          elif len(auth) > 2:
              msg = _("Invalid basic header. Credentials string should not contain spaces.")
              raise exceptions.AuthenticationFailed(msg)
  
 
</s> remove             msg = _("Invalid token header. No credentials provided.")
 </s> add             msg = _('Invalid token header. No credentials provided.') </s> remove             msg = _("Invalid basic header. Credentials string should not contain spaces.")
 </s> add             msg = _('Invalid basic header. Credentials string should not contain spaces.') </s> remove             msg = _("Invalid token header. Token string should not contain spaces.")
 </s> add             msg = _('Invalid token header. Token string should not contain spaces.') </s> remove             msg = _("Invalid basic header. Credentials not correctly base64 encoded.")
 </s> add             msg = _('Invalid basic header. Credentials not correctly base64 encoded.') </s> remove                     msg = _("User account is disabled.")
 </s> add                     msg = _('User account is disabled.')
            msg = _('Invalid basic header. No credentials provided.')
          if not auth or auth[0].lower() != b'basic':
              return None
  
          if len(auth) == 1:
            msg = _('Invalid basic header. No credentials provided.')
              raise exceptions.AuthenticationFailed(msg)
          elif len(auth) > 2:
              msg = _("Invalid basic header. Credentials string should not contain spaces.")
              raise exceptions.AuthenticationFailed(msg)
  
keep keep keep keep replace keep keep keep keep keep
 prefer single quotes in source and double quotes in user visible strings; add some missing full stops to user visible strings 
rest_framework/authentication.py