Martin von Zweigbergk <martinvonz@google.com> [Wed, 09 Dec 2020 19:40:30 -0800] rev 46116
errors: use detailed exit code 50 for StorageError
This is done as part of
https://www.mercurial-scm.org/wiki/ErrorCategoriesPlan.
Differential Revision: https://phab.mercurial-scm.org/D9601