sftp: raise BackendDoesNotExist if base path is not found

src/borgstore/backends/sftp.py

@@ -130,7 +130,10 @@ def open(self):
  if self.opened:
  raise BackendMustNotBeOpen()
  self._connect()
- st = self.client.stat(self.base_path) # check if this storage exists, fail early if not.
+ try:
+ st = self.client.stat(self.base_path) # check if this storage exists, fail early if not.
+ except FileNotFoundError:
+ raise BackendDoesNotExist(f"sftp storage base path does not exist: {self.base_path}")
  if not stat.S_ISDIR(st.st_mode):
  raise BackendDoesNotExist(f"sftp storage base path is not a directory: {self.base_path}")
  self.client.chdir(self.base_path) # this sets the cwd we work in!