Unhandled `KeyStoreError` in `git-secret check` for missing secret key.

[sg495]

❯ git-secret check
❌🔑 missing secret key: File .mnemonic not found.
Traceback (most recent call last):
  File "<frozen runpy>", line 198, in _run_module_as_main
  File "<frozen runpy>", line 88, in _run_code
  File "...\git-secret.exe\__main__.py", line 8, in <module>
  File "...\git_secret\script.py", line 269, in main
    filestore.check(args.filenames, deep=args.deep)
  File "...\git_secret\filestore.py", line 120, in check
    return self.__apply_file_op(
           ^^^^^^^^^^^^^^^^^^^^^
  File "...\git_secret\filestore.py", line 544, in __apply_file_op
    files = self.managed_files
            ^^^^^^^^^^^^^^^^^^
  File "...\git_secret\filestore.py", line 41, in managed_files
    self.__load()
  File "...\git_secret\filestore.py", line 604, in __load
    key = self.keystore.key
          ^^^^^^^^^^^^^^^^^
  File "...\git_secret\keystore.py", line 45, in key
    self.__load()
  File "...\git_secret\keystore.py", line 130, in __load
    raise KeyStoreError(f"File {mnemonic_filename} not found.")
git_secret.keystore.KeyStoreError: File .mnemonic not found.