upgrade: byteify a few error messages

These were flagged by pytype (which is currently disabled on this file due to
another failure).

Differential Revision: https://phab.mercurial-scm.org/D11905

mercurial/upgrade.py

@@ -278,7 +278,7 b' def upgrade_share_to_safe('
         ui.warn(_(b'repository upgraded to use share-safe mode\n'))
     except error.LockError as e:
         hint = _(
-            "see `hg help config.format.use-share-safe` for more information"
+            b"see `hg help config.format.use-share-safe` for more information"
         )
         if mismatch_config == b'upgrade-abort':
             raise error.Abort(
@@ -335,7 +335,7 b' def downgrade_share_to_non_safe('
         ui.warn(_(b'repository downgraded to not use share-safe mode\n'))
     except error.LockError as e:
         hint = _(
-            "see `hg help config.format.use-share-safe` for more information"
+            b"see `hg help config.format.use-share-safe` for more information"
         )
         # If upgrade-abort is set, abort when upgrade fails, else let the
         # process continue as `upgrade-allow` is set