Account for new psycopg2 exception classes mapping From psycopg2 >= 2.8, specific exceptions are raised corresponding to postgresql errors. E.g. a CheckViolation exception is raised instead of a generic IntegrityError previously when a constraint violation occurs. The way we intercept database errors, especially for constraint violation, is not compliant with that because we do not catch subclasses of IntegrityError in native source's doexec() method. We fix this by checking for the presence of IntegrityError error in exception class's mro. This is still overcomplicated and clumsy, because we still use string comparison, but this is the best we can do as far as I know. (A better fix would be 'isinstance(ex, IntegrityError)' but we have no engine-independent error classes, so this is not possible. Something like sqlalchemy's DBAPI Errors [1] might help: https://docs.sqlalchemy.org/en/latest/errors.html#dbapi-errors)

CSS Coding Standards
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(Draft, to be continued)

:Naming: camelCase

Indentation rules
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- 2 spaces before properties

- no space before ":", one space after

- only one space between values of the same property


Documentation
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Please keep rules semantically linked grouped together, with a comment about
what they are for.

Recommendation
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- Try to use existing classes rather than introduce new ones

- Keep things as simple as possible while in the framework

- Think about later customization by application

- Avoid introducing a new CSS file for a few lines of CSS, at least while the
  framework doesn't include packing functionalities