v1.9.0 Dropped 3.6 support and reduced code size

What's Changed

We bumped the version of the upstream and dependencies. The new pyo3 dropped py36 support.
We also improved the error handling in the codebase by using more elegant syntaxes, which significantly reduced code duplication.

• Bump upstream and cleanup error handling by @ChihChengLiang in #38

Full Changelog: v1.8.1...v1.9.0