storageutil: consistently raise LookupError (API)

The interface docs say this is supposed to raise LookupError on
failure. But for invalid revision number input, it could raise
IndexError because ifileindex.node() is documented to raise
IndexError.

lookup() for files isn't used that much (pretty much just in
basefilectx in core AFAICT). And callers should already be catching
LookupError. So I don't anticipate that much fallout from this
change.

Differential Revision: https://phab.mercurial-scm.org/D4798

mercurial/testing/storage.py

@@ -199,13 +199,13 b' class ifileindextests(basetestcase):'
         with self.assertRaises(error.LookupError):
             f.lookup(hex(node)[0:12])
 
-        with self.assertRaises(IndexError):
+        with self.assertRaises(error.LookupError):
             f.lookup(-2)
 
         with self.assertRaises(error.LookupError):
             f.lookup(b'-2')
 
-        with self.assertRaises(IndexError):
+        with self.assertRaises(error.LookupError):
             f.lookup(1)
 
         with self.assertRaises(error.LookupError):

mercurial/utils/storageutil.py

@@ -121,7 +121,10 b' def fileidlookup(store, fileid, identifi'
     Raises ``error.LookupError`` on failure.
     """
     if isinstance(fileid, int):
-        return store.node(fileid)
+        try:
+            return store.node(fileid)
+        except IndexError:
+            raise error.LookupError(fileid, identifier, _('no match found'))
 
     if len(fileid) == 20:
         try: