Martin von Zweigbergk <martinvonz@google.com> [Fri, 14 Jan 2022 08:44:36 -0800] rev 48565
simplemerge: delete unused exception class `CantReprocessAndShowBase`
The only user was removed in f18830651811 (simplemerge: burn "minimal"
feature to the ground, 2014-08-05).
Differential Revision: https://phab.mercurial-scm.org/D11998