text: Title: Get an error run `scripts/test` in a newly cloned `uvicorn`
  Body: ### Discussed in https://github.com/encode/uvicorn/discussions/1755
  
  <div type='discussions-op-text'>
  
  <sup>Originally posted by **ys-wu** November  2, 2022</sup>
  I clone my fork: 
  ```
  git clone https://github.com/MY-USERNAME/uvicorn
  ```
  
  Then simply install and test:
  ```
  cd uvicorn
  scripts/install
  scripts/test
  ```
  
  And get the error:
  ```
  + '[' -z ']'
  + scripts/check
  + ./scripts/sync-version
  + venv/bin/black --check --diff --target-version=py37 uvicorn tests
  All done! ✨ 🍰 ✨
  63 files would be left unchanged.
  + venv/bin/flake8 uvicorn tests
  + venv/bin/mypy --show-error-codes
  Success: no issues found in 53 source files
  + venv/bin/isort --check --diff --project=uvicorn uvicorn tests
  + venv/bin/python -m tools.cli_usage --check
  Traceback (most recent call last):
    File "<frozen runpy>", line 198, in _run_module_as_main
    File "<frozen runpy>", line 88, in _run_code
    File "/Users/wuyusheng/playground/uvicorn/tools/cli_usage.py", line 69, in <module>
      rv |= _generate_cli_usage(path, check=args.check)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/Users/wuyusheng/playground/uvicorn/tools/cli_usage.py", line 47, in _generate_cli_usage
      usage_lines = _get_usage_lines()
                    ^^^^^^^^^^^^^^^^^^
    File "/Users/wuyusheng/playground/uvicorn/tools/cli_usage.py", line 13, in _get_usage_lines
      res = subprocess.run(["uvicorn", "--help"], stdout=subprocess.PIPE)
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/Users/wuyusheng/.pyenv/versions/3.11.0/lib/python3.11/subprocess.py", line 546, in run
      with Popen(*popenargs, **kwargs) as process:
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^
    File "/Users/wuyusheng/.pyenv/versions/3.11.0/lib/python3.11/subprocess.py", line 1022, in __init__
      self._execute_child(args, executable, preexec_fn, close_fds,
    File "/Users/wuyusheng/.pyenv/versions/3.11.0/lib/python3.11/subprocess.py", line 1899, in _execute_child
      raise child_exception_type(errno_num, err_msg, err_filename)
  FileNotFoundError: [Errno 2] No such file or directory: 'uvicorn'
  ```
  
  My environment:
  ```
  MacBook Pro 2017
  macOS Monterey Version 12.6 (21G115)
  Python 3.11.0
  ```
  
  </div>