Use pyproject file for project metadata.

[naschmitz]

Motivation:

• Official Python support for packages using setup.py are in varying states of deprecation.
• The Python packaging guide strongly recommends a pyproject.toml file.
• Enables release automation not possible before (e.g. setuptools_scm).

Summary of changes:

• Switches metadata to pyproject.toml instead of setup.py and setup.cfg files.
• Upgraded bump2version (unmaintained) to bump-my-version.
  • Usage is similar. In command-line calls, replace bumpversion with bump-my-version.
• Switched from flake8 to pyproject-flake8.
  • Usage is similar. In command-line calls, replace flake8 with pflake8.
• Updated all the relevant documentation.

[schwehr]

One minor change and a few suggestions for follow on PRs

[schwehr]

Not for the commit, but setting up https://github.com/pre-commit/pre-commit or simillar would be a good idea to automate this kind of cleanup

[naschmitz]

Ack. Good idea!

[schwehr]

Out of scope for here, but the keyword list needs to be expanded

[schwehr]

Out of scope for here, but the classifiers needs to be expanded

[giswqs]

@naschmitz Great work! I have many Python packages that also need the migration. This is a great example I can learn from. Thank you very much!

[giswqs]

@naschmitz I just realized that the wheel generated by python -m build is missing the source file in it, causing the import geemap to fail. Not sure if we can modify the pyproject.toml to including the source files. Investigating.