[MIG] 12.0 super_calendar

[diggy128]

• Fixed some minor Python2 > 3 issues.
• Odoo keeps microseconds for write_date and create_date fields and drops them for Datetime fields. As so, in order for duration to be consistent, microseconds are dropped entire to allow using any datetime field.
• Updated file headers and README to be consistent with OCA guidelines.

I should mention migration in based on @jeanpaulrobineau and PR #609 for v10.0

[thomaspaulb]

/ocabot rebase

[OCA-git-bot]

Congratulations, PR rebased to 12.0.

[thomaspaulb]

@diggy128 Seems flake8 is complaining about some unused imports.

[github-actions]

There hasn't been any activity on this pull request in the past 4 months, so it has been marked as stale and it will be closed automatically if no further activity occurs in the next 30 days.
If you want this PR to never become stale, please ask a PSC member to apply the "no stale" label.