support str or promise in errors (#1319)

Author: mschoettle

django-stubs/core/exceptions.pyi

@@ -31,7 +31,7 @@ NON_FIELD_ERRORS: Literal["__all__"]
 class ValidationError(Exception):
     error_dict: dict[str, list[ValidationError]]
     error_list: list[ValidationError]
-    message: str
+    message: _StrOrPromise
     code: str | None
     params: dict[str, Any] | None
     def __init__(

django-stubs/forms/forms.pyi

@@ -7,6 +7,7 @@ from django.forms.fields import Field
 from django.forms.renderers import BaseRenderer
 from django.forms.utils import ErrorDict, ErrorList, _DataT, _FilesT
 from django.forms.widgets import Media, MediaDefiningClass
+from django.utils.functional import _StrOrPromise
 from django.utils.safestring import SafeString
 
 class DeclarativeFieldsMetaclass(MediaDefiningClass): ...
@@ -55,7 +56,7 @@ class BaseForm:
     def as_ul(self) -> SafeString: ...
     def as_p(self) -> SafeString: ...
     def non_field_errors(self) -> ErrorList: ...
-    def add_error(self, field: str | None, error: ValidationError | str) -> None: ...
+    def add_error(self, field: str | None, error: ValidationError | _StrOrPromise) -> None: ...
     def has_error(self, field: str | None, code: str | None = ...) -> bool: ...
     def full_clean(self) -> None: ...
     def clean(self) -> dict[str, Any] | None: ...