Preserve local password for shibboleth users

Bug #2535

snf-astakos-app/astakos/im/forms.py

@@ -318,6 +318,12 @@ class LoginForm(AuthenticationForm):
         check = captcha.submit(rcf, rrf, RECAPTCHA_PRIVATE_KEY, self.ip)
         if not check.is_valid:
             raise forms.ValidationError(_('You have not entered the correct words'))
+    
+    def clean(self):
+        super(LoginForm, self).clean()
+        if self.user_cache.provider != 'local':
+            raise forms.ValidationError(_('Local login is not the current authentication method for this account.'))
+        return self.cleaned_data
 
 class ProfileForm(forms.ModelForm):
     """

snf-astakos-app/astakos/im/functions.py

@@ -258,7 +258,6 @@ def switch_account_to_shibboleth(user, local_user, greeting_template_name='im/we
     
     user.delete()
     local_user.provider = 'shibboleth'
-    local_user.set_unusable_password()
     local_user.third_party_identifier = user.third_party_identifier
     local_user.save()
     send_greeting(local_user, greeting_template_name)