Inelegant failure after first install

[nedbat]

• Install scriv 0.8.0
• Run "scriv create"
• Look:

  $ scriv create
  Creating changelog.d/20200804_133229_nedbat.rst
  Traceback (most recent call last):
  File "/usr/local/virtualenvs/webhooks/bin/scriv", line 8, in <module>
  sys.exit(cli())
  File "/usr/local/virtualenvs/webhooks/lib/python3.8/site-packages/click/core.py", line 829, in __call__
  return self.main(*args, **kwargs)
  File "/usr/local/virtualenvs/webhooks/lib/python3.8/site-packages/click/core.py", line 782, in main
  rv = self.invoke(ctx)
  File "/usr/local/virtualenvs/webhooks/lib/python3.8/site-packages/click/core.py", line 1259, in invoke
  return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/usr/local/virtualenvs/webhooks/lib/python3.8/site-packages/click/core.py", line 1066, in invoke
  return ctx.invoke(self.callback, **ctx.params)
  File "/usr/local/virtualenvs/webhooks/lib/python3.8/site-packages/click/core.py", line 610, in invoke
  return callback(*args, **kwargs)
  File "/usr/local/virtualenvs/webhooks/lib/python3.8/site-packages/scriv/create.py", line 60, in create
  with open(file_path, "w") as f:
  FileNotFoundError: [Errno 2] No such file or directory: 'changelog.d/20200804_133229_nedbat.rst'

[nedbat]

Fixed in 351ba2e4034caa800742ca427e9043ef71ae03d4.