Summary: Verify certificates using native system trust stores

Description:
Truststore is a library which exposes native system certificate stores (ie trust
stores) through an ssl.SSLContext-like API. This means that Python applications
no longer need to rely on certifi as a root certificate store. Native system
certificate stores have many helpful features compared to a static certificate
bundle like certifi:

- Automatically update certificates as new CAs are created and removed
- Fetch missing intermediate certificates
- Check certificates against certificate revocation lists (CRLs) to avoid
monster-in-the-middle (MITM) attacks
- Managed per-system rather than per-application by a operations/IT team
- PyPI is no longer a CA distribution channel

Maintainer: papoteur