[Enhance] Enhance error report when a module has been registered in registery. (#264)

* Update

* Add unittest

mmengine/registry/registry.py

@@ -480,8 +480,9 @@ class Registry:
             module_name = [module_name]
         for name in module_name:
             if not force and name in self._module_dict:
-                raise KeyError(f'{name} is already registered '
-                               f'in {self.name}')
+                existed_module = self.module_dict[name]
+                raise KeyError(f'{name} is already registered in {self.name} '
+                               f'at {existed_module.__module__}')
             self._module_dict[name] = module_class
 
     def register_module(

tests/test_registry/test_registry.py

@@ -115,7 +115,8 @@ class TestRegistry:
         # force=False
         with pytest.raises(
                 KeyError,
-                match='BritishShorthair is already registered in cat'):
+                match='BritishShorthair is already registered in cat '
+                'at test_registry'):
 
             @CATS.register_module()
             class BritishShorthair: