refactor error callback (#1)

Author: belm0

mypy/main.py

@@ -1458,13 +1458,14 @@ def set_strict_flags() -> None:
 
     options.process_incomplete_features(error_callback=parser.error, warning_callback=print)
 
-    def on_plugins_loaded() -> None:
-        # Processing error codes after plugins have loaded since plugins may
-        # register custom error codes that we don't know about until plugins
-        # have loaded.
-        options.process_error_codes(error_callback=parser.error)
-
-    options._on_plugins_loaded = on_plugins_loaded
+    def _bad_error_code_flags(msg: str):
+        raise CompileError([msg])
+
+    # Processing error codes after plugins have loaded since plugins may
+    # register custom error codes that we don't know about until plugins
+    # have loaded.
+    options._on_plugins_loaded = \
+        lambda: options.process_error_codes(error_callback=_bad_error_code_flags)
 
     # Compute absolute path for custom typeshed (if present).
     if options.custom_typeshed_dir is not None: