cmdutil: add a pytype annotation to help out some callsites

I think we could constrain the values here more than Any, but this
lets us move forward with typechecking commands.py.

Differential Revision: https://phab.mercurial-scm.org/D7381

mercurial/cmdutil.py

@@ -61,6 +61,15 b' from .utils import ('
     stringutil,
 )
 
+if not globals():
+    from typing import (
+        Any,
+        Dict,
+    )
+
+    for t in (Any, Dict):
+        assert t
+
 stringio = util.stringio
 
 # templates of common command options
@@ -3959,6 +3968,7 b' def abortgraft(ui, repo, graftstate):'
 
 
 def readgraftstate(repo, graftstate):
+    # type: (Any, statemod.cmdstate) -> Dict[bytes, Any]
     """read the graft state file and return a dict of the data stored in it"""
     try:
         return graftstate.read()