Update sqlalchemy requirement from ~=1.3.20 to ~=1.3.21

[dependabot]

Updates the requirements on sqlalchemy to permit the latest version.

Release notes

Sourced from sqlalchemy's releases.

1.3.21

Released: December 17, 2020

orm

• [orm] [bug] Added a comprehensive check and an informative error message for the case where a mapped class, or a string mapped class name, is passed to _orm.relationship.secondary. This is an extremely common error which warrants a clear message.

  Additionally, added a new rule to the class registry resolution such that with regards to the _orm.relationship.secondary parameter, if a mapped class and its table are of the identical string name, the Table will be favored when resolving this parameter. In all other cases, the class continues to be favored if a class and table share the identical name.

  References: #5774

• [orm] [bug] Fixed bug in _query.Query.update() where objects in the _ormsession.Session that were already expired would be unnecessarily SELECTed individually when they were refreshed by the "evaluate"synchronize strategy.

  References: #5664

• [orm] [bug] Fixed bug involving the restore_load_context option of ORM events such as _ormevent.InstanceEvents.load() such that the flag would not be carried along to subclasses which were mapped after the event handler were first established.

  References: #5737

sql

• [sql] [bug] A warning is emmitted if a returning() method such as _sql.Insert.returning() is called multiple times, as this does not yet support additive operation. Version 1.4 will support additive operation for this. Additionally, any combination of the _sql.Insert.returning() and _sql.ValuesBase.return_defaults() methods now raises an error as these methods are mutually exclusive; previously the operation would fail silently.

  References: #5691

• [sql] [bug] Fixed structural compiler issue where some constructs such as MySQL / PostgreSQL "on conflict / on duplicate key" would rely upon the state of

... (truncated)

Commits

• See full diff in compare view

Dependabot will resolve any conflicts with this PR as long as you don't alter it yourself. You can also trigger a rebase manually by commenting @dependabot rebase.

---

Dependabot commands and options

You can trigger Dependabot actions by commenting on this PR:

• @dependabot rebase will rebase this PR
• @dependabot recreate will recreate this PR, overwriting any edits that have been made to it
• @dependabot merge will merge this PR after your CI passes on it
• @dependabot squash and merge will squash and merge this PR after your CI passes on it
• @dependabot cancel merge will cancel a previously requested merge and block automerging
• @dependabot reopen will reopen this PR if it is closed
• @dependabot close will close this PR and stop Dependabot recreating it. You can achieve the same result by closing it manually
• @dependabot ignore this major version will close this PR and stop Dependabot creating any more for this major version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this minor version will close this PR and stop Dependabot creating any more for this minor version (unless you reopen the PR or upgrade to it yourself)
• @dependabot ignore this dependency will close this PR and stop Dependabot creating any more for this dependency (unless you reopen the PR or upgrade to it yourself)