storageutil: consistently raise LookupError (API)

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

--- a/mercurial/testing/storage.py	Fri Sep 28 11:03:17 2018 -0700
+++ b/mercurial/testing/storage.py	Fri Sep 28 11:16:44 2018 -0700
@@ -199,13 +199,13 @@
         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):

--- a/mercurial/utils/storageutil.py	Fri Sep 28 11:03:17 2018 -0700
+++ b/mercurial/utils/storageutil.py	Fri Sep 28 11:16:44 2018 -0700
@@ -121,7 +121,10 @@
     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: