Include name of missing hook in HookMissing

Author: chrahunt

pep517/wrappers.py

@@ -37,6 +37,9 @@ def __init__(self, backend_name, backend_path, message):
 
 class HookMissing(Exception):
     """Will be raised on missing hooks."""
+    def __init__(self, hook_name):
+        super(HookMissing, self).__init__(hook_name)
+        self.hook_name = hook_name
 
 
 class UnsupportedOperation(Exception):
@@ -245,7 +248,7 @@ def _call_hook(self, hook_name, kwargs):
                     message=data.get('backend_error', '')
                 )
             if data.get('hook_missing'):
-                raise HookMissing()
+                raise HookMissing(hook_name)
             return data['return_val']
 
 

tests/test_hook_fallbacks.py

@@ -45,7 +45,11 @@ def test_prepare_metadata_for_build_wheel_no_fallback():
 
     with TemporaryDirectory() as metadatadir:
         with modified_env({'PYTHONPATH': BUILDSYS_PKGS}):
-            with pytest.raises(HookMissing):
+            with pytest.raises(HookMissing) as exc_info:
                 hooks.prepare_metadata_for_build_wheel(
                     metadatadir, {}, _allow_fallback=False
                 )
+
+            e = exc_info.value
+            assert 'prepare_metadata_for_build_wheel' == e.hook_name
+            assert 'prepare_metadata_for_build_wheel' in str(e)