Roll //third_party/typ to v0.9.9

third_party/typ/typ/arg_parser.py

Index: third_party/typ/typ/arg_parser.py
diff --git a/third_party/typ/typ/arg_parser.py b/third_party/typ/typ/arg_parser.py
index f7a602669816bdd4327fde54febd8972bbb70a9d..31d575d879e4c31e6a432379ac1db712e4d9efdc 100644
--- a/third_party/typ/typ/arg_parser.py
+++ b/third_party/typ/typ/arg_parser.py
@@ -280,6 +280,8 @@ class ArgumentParser(argparse.ArgumentParser):
             v = d[k]
             argname = _argname_from_key(k)
             action = self._action_for_key(k)
+            if not action:
+                continue
             action_str = _action_str(action)
             if k == 'tests':
                 tests = v
@@ -310,8 +312,9 @@ class ArgumentParser(argparse.ArgumentParser):
             if action.dest == key:
                 return action
 
-        assert False, ('Could not find an action for %s'  # pragma: no cover
-                       % key)
+        # Assume foreign argument: something used by the embedder of typ, for
+        # example.
+        return None
 
 
 def _action_str(action):