Could not work with pyton-dotenv>=0.19.0

[davidlatwe]

If recipe rezup.toml has section env, rezup could not use container due to some change made in pyton-dotenv-0.19.0

C:\Users\david>rezup
Traceback (most recent call last):
  File "c:\python37\lib\runpy.py", line 193, in _run_module_as_main
    "__main__", mod_spec)
  File "c:\python37\lib\runpy.py", line 85, in _run_code
    exec(code, run_globals)
  File "C:\Python37\Scripts\rezup.exe\__main__.py", line 7, in <module>
  File "c:\users\david\dev\rezup\src\rezup\cli.py", line 100, in run
    cmd_use(opts.name, job=opts.do)
  File "c:\users\david\dev\rezup\src\rezup\cli.py", line 118, in cmd_use
    revision.use(run_script=job)
  File "c:\users\david\dev\rezup\src\rezup\container.py", line 420, in use
    environment = self._compose_env()
  File "c:\users\david\dev\rezup\src\rezup\container.py", line 462, in _compose_env
    env.update(self.recipe_env() or {})
  File "c:\users\david\dev\rezup\src\rezup\container.py", line 350, in recipe_env
    recipe_env_dict = dotenv_values(buffer)  # noqa
  File "c:\python37\lib\site-packages\dotenv\main.py", line 359, in dotenv_values
    encoding=encoding,
  File "c:\python37\lib\site-packages\dotenv\main.py", line 74, in dict
    self._dict = OrderedDict(resolve_variables(raw_values, override=self.override))
  File "c:\python37\lib\site-packages\dotenv\main.py", line 218, in resolve_variables
    for (name, value) in values:
  File "c:\python37\lib\site-packages\dotenv\main.py", line 81, in parse
    with self._get_stream() as stream:
  File "c:\python37\lib\contextlib.py", line 112, in __enter__
    return next(self.gen)
  File "c:\python37\lib\site-packages\dotenv\main.py", line 53, in _get_stream
    if self.dotenv_path and os.path.isfile(self.dotenv_path):
  File "c:\python37\lib\genericpath.py", line 30, in isfile
    st = os.stat(path)
TypeError: stat: path should be string, bytes, os.PathLike or integer, not _io.StringIO