localrepo: fix conversion of exceptions to strings flagged by pytype

This is the same as e571fec5b606.  I assume the 3 similar uses of `bytestr` in
`__getitem__()` are OK (even though pytype also flags them), because there is
apparently test coverage for 2 of the 3 cases.

Differential Revision: https://phab.mercurial-scm.org/D10131

mercurial/localrepo.py

@@ -540,7 +540,7 b' def makelocalrepository(baseui, path, in'
         except ValueError as e:
             # Can be raised on Python 3.8 when path is invalid.
             raise error.Abort(
-                _(b'invalid path %s: %s') % (path, pycompat.bytestr(e))
+                _(b'invalid path %s: %s') % (path, stringutil.forcebytestr(e))
             )
 
         raise error.RepoError(_(b'repository %s not found') % path)