Log stat errors

Author: Zac-HD

mypy/build.py

@@ -1314,6 +1314,7 @@ def validate_meta(meta: Optional[CacheMeta], id: str, path: Optional[str],
         try:
             data_mtime = manager.getmtime(meta.data_json)
         except OSError:
+            manager.log('Metadata abandoned for {}: failed to stat data_json'.format(id, path))
             return None
         if data_mtime != meta.data_mtime:
             manager.log('Metadata abandoned for {}: data cache is modified'.format(id))
@@ -1530,6 +1531,7 @@ def write_cache(id: str, path: str, tree: MypyFile,
     try:
         data_mtime = manager.getmtime(data_json)
     except OSError:
+        manager.log("Error in os.stat({!r}), skipping cache write".format(data_json))
         return interface_hash, None
 
     mtime = 0 if bazel else int(st.st_mtime)