GitLab

The documentation is now generated automatically for each tag
via GitLab CI.

Install importlib-metadata in CI (missing dependency for pip-tools: https://github.com/jazzband/pip-tools/issues/1352)

The exception MissingAugmentTarget was completely removed. A missing
augment target is now silently ignored.

Brackets are no more appropriate as they can appear in an i-i.

Unset IGNORE_EXCEPTION_DETAIL in doctest_default_flags.

Fixes GitHub issues #86, #91 and #95.

This prevents the doctest for orphan_instance method from failing.

These exception classes now have the offending InstanceNode as
their member (instead of its JSONPointer), so it is easier for
exception handlers to inspect the instance.

This change also affects the following subclasses:
* InstanceValueError
* NonexistentInstance
* NonDataNode
* SchemaError
* SemanticError

Simplify XML handling and cleanup notification usecase

Fix notification generation and remove allow_nodata parameter
Fix detection of no text for empty type