errors: create superclass for Abort exception...
errors: create superclass for Abort exception
I'd like to let extensions subclass `StorageError` to define a custom
exit code. However, `StorageError` does not extend `Abort` (which is
where the exit code currently lives), and it seems that it's not
supposed to either (`StorageError` seems to be for lower-level errors
and `Abort` is for command-level errors). This patch therefore
extracts all the code from `Abort` into a new `Error` class, which
I'll soon make `StorageError` also extend.
Differential Revision:
https://phab.mercurial-scm.org/D10738
