Environs

- Improve typings and run mypy with dependencies type annotations ([115](https://github.com/sloria/environs/pull/115)).
- Distribute types per PEP 561 ([116](https://github.com/sloria/environs/pull/116)).

Thanks [hukkinj1](https://github.com/hukkinj1) for the PRs.

- _Backwards-incompatible_: Remove `stream` argument from `read_env`,
since it had no effect ([114](https://github.com/sloria/environs/pull/114)).
- _Backwards-incompatible_: `Env.read_env` consistently returns `None`
([111](https://github.com/sloria/environs/pull/111)).
- Remove unnecessary `__str__` definition ([112](https://github.com/sloria/environs/pull/112)).

Thanks [hukkinj1](https://github.com/hukkinj1) for the PRs.

Features:

- Add deferred validation via the `eager` parameter and `env.seal()` ([56](https://github.com/sloria/environs/issues/56)).
Thanks [robertlagrant](https://github.com/robertlagrant) for the suggestion.

Other changes:

- Test against Python 3.8 ([108](https://github.com/sloria/environs/pull/108)).

Features:

- Default parser methods are now defined as bound methods.
This enables static analysis features, e.g. autocomplete ([103](https://github.com/sloria/environs/issues/103)).
Thanks [rugleb](https://github.com/rugleb) for the suggestion.
_Backwards-incompatible_: As a result of this change, adding a parser name that is the same as an existing method
will result in an error being raised.

python
import environs

env = environs.Env()


Below conflicts with built-in `url` method.
In <6.0.0, this would override the built-in method.
In >=6.0.0, this raises an error:
environs.ParserConflictError: Env already has a method with name 'url'. Use a different name.
env.parser_for("url")
def https_url(value):
return "https://" + value


Bug fixes:

- Fix error message for prefixed variables ([102](https://github.com/sloria/environs/issues/102)).
Thanks [AGeekInside](https://github.com/AGeekInside) for reporting.

Other changes:

- _Backwards-incompatible_: Rename `Env.__parser_map__` to `Env.__custom_parsers__`.

Bug fixes:

- Fix behavior when recursively searching for a specified file
([96](https://github.com/sloria/environs/issues/96)).
Thanks [ribeaud](https://github.com/ribeaud) for the catch and patch.

Changes:

- Improve typings.