auth: Include user-input email in some error messages in the login form.

Fixes #13126.

zerver/forms.py

@@ -49,12 +49,12 @@ MIT_VALIDATION_ERROR = (
     + '<a href="mailto:support@zulip.com">contact us</a>.'
 )
 WRONG_SUBDOMAIN_ERROR = (
-    "Your Zulip account is not a member of the "
+    "Your Zulip account {username} is not a member of the "
     + "organization associated with this subdomain.  "
     + "Please contact your organization administrator with any questions."
 )
 DEACTIVATED_ACCOUNT_ERROR = (
-    "Your account is no longer active. "
+    "Your account {username} is no longer active. "
     + "Please contact your organization administrator to reactivate it."
 )
 PASSWORD_RESET_NEEDED_ERROR = (
@@ -432,13 +432,15 @@ class OurAuthenticationForm(AuthenticationForm):
                 # We exclude mirror dummy accounts here. They should be treated as the
                 # user never having had an account, so we let them fall through to the
                 # normal invalid_login case below.
-                raise ValidationError(mark_safe(DEACTIVATED_ACCOUNT_ERROR))
+                error_message = DEACTIVATED_ACCOUNT_ERROR.format(username=username)
+                raise ValidationError(mark_safe(error_message))
 
             if return_data.get("invalid_subdomain"):
                 logging.warning(
                     "User %s attempted password login to wrong subdomain %s", username, subdomain
                 )
-                raise ValidationError(mark_safe(WRONG_SUBDOMAIN_ERROR))
+                error_message = WRONG_SUBDOMAIN_ERROR.format(username=username)
+                raise ValidationError(mark_safe(error_message))
 
             if self.user_cache is None:
                 raise forms.ValidationError(