Dactyl

This release fixes a bug with the link checker where it would try (and fail) to check links with absolute paths if those links had anchors in them. It now correctly skips links with absolute paths regardless of whether they have anchors.

This release fixes a file-decoding bug on Windows. It also incorporates the changes from (unreleased) v0.8.1, which quiets CSS warnings from Prince.

v0.8.0 updates the requirements for Dactyl, fixes some bugs, and adds some small features.

**Updated Dependencies**

- **Python v3.5 or higher** is now required.
- Changes to ruamel.yaml from from PyYAML since PyYAML is not much maintained.
- Updates to the latest versions of other packages.

**Breaking Changes:**

- Dactyl now raises an error when it reads a YAML config file with any duplicate keys. You can use `--bypass_errors` to skip past these errors and use the first instance of each key only. (Previously, Dactyl used only the last instance of any duplicate keys.)
- YAML Config files are now loaded in "safe" mode.

**New and updated features:**

- Adds the option to use "strict" undefined fields in templates or the preprocessor. This raises an error if you refer to a field that's undefined. (By default, Dactyl ignores keys that are not defined in both preprocessor and template syntax.)
Use `--template_strict_undefined` on the commandline or `template_allow_undefined = false` in the config file to enable strict undefined for templates. Use `--pp_strict_undefined` on the commandline or `preprocessor_allow_undefined = false` in the config file to enable strict undefined for the preprocessor.
- Adds two new custom tests to the templating syntax: `defined_and_equalto` and `undefined_or_ne`. These tests combine existing Jinja tests for to make it easier to use [`selectattr()`](http://jinja.pocoo.org/docs/2.10/templates/#selectattr) on the `pages` array when using strict undefined is enabled.

**Bug Fixes:**

- Fixes namespace overlapping when loading more than one custom filter at a time. This previously could cause some custom filters' effects to run twice or not at all.
- Duplicate keys in YAML files are no longer ignored.

This minor release fixes the link substitution filter's behavior in Markdown mode, and more gracefully handles config files that list missing files without explicit page titles.

This patch release provides more information in the error message when template/preprocessor parsing encounters an error.

This minor upgrade improves the flexibility of the ElasticSearch uploader introduced in Dactyl v0.7.0 (the `--es_upload` command).

This version supports new config options, `es_index_fields` and `es_index_separator` which are analogous to `pdf_filename_fields` and `pdf_filename_separator` but for generating the names of indexes where Dactyl uploads things to ElasticSearch. Previously, Dactyl used the same formula for both PDF filenames and ElasticSearch index names.

**Caution:** If you are using the ElasticSearch uploader and non-default values for `pdf_filename_fields` or `pdf_filename_separator`, Dactyl v0.7.1 uploads files to different ES indexes than Dactyl v0.7.0 unless you also define the `es_index_fields` and `es_index_separator` config fields to match.

There are no other changes to Dactyl functionality so there's no need to upgrade from 0.7.0 if you're not using Dactyl's ElasticSearch uploader.