correct imports, fix #420 (#423)

pydantic/__init__.py

@@ -1,4 +1,5 @@
 # flake8: noqa
+from . import dataclasses
 from .class_validators import validator
 from .env_settings import BaseSettings
 from .error_wrappers import ValidationError
@@ -6,7 +7,6 @@ from .errors import *
 from .fields import Required
 from .main import BaseConfig, BaseModel, Extra, create_model, validate_model
 from .parse import Protocol
+from .schema import Schema
 from .types import *
 from .version import VERSION
-from . import dataclasses
-from .schema import Schema

pydantic/dataclasses.py

@@ -1,7 +1,8 @@
 import dataclasses
 from typing import TYPE_CHECKING, Any, Callable, Dict, Generator, Optional, Type, Union
 
-from . import ValidationError, errors
+from .error_wrappers import ValidationError
+from .errors import DataclassTypeError
 from .main import create_model, validate_model
 from .utils import AnyType
 
@@ -37,7 +38,7 @@ def _validate_dataclass(cls: Type['DataclassType'], v: Any) -> 'DataclassType':
     elif isinstance(v, dict):
         return cls(**v)
     else:
-        raise errors.DataclassTypeError(class_name=cls.__name__)
+        raise DataclassTypeError(class_name=cls.__name__)
 
 
 def _get_validators(cls: Type['DataclassType']) -> Generator[Any, None, None]: