This PR was merged into the 4.2 branch.Discussion----------Add missing rendering of form help block.| Q             | A| ------------- | ---| Branch?       | 4.2 <!-- see below -->| Bug fix?      | yes| New feature?  | no <!-- please update src/**/CHANGELOG.md files -->| BC breaks?    | no     <!-- seehttps://symfony.com/bc -->| Deprecations? | no <!-- please update UPGRADE-*.md and src/**/CHANGELOG.md files -->| Tests pass?   | yes    <!-- please add some, will be required by reviewers -->| License       | MIT<!--Replace this notice by a short README for your feature/bugfix. This will help peopleunderstand your PR and can be used as a start for the documentation.Additionally (seehttps://symfony.com/roadmap): - Bug fixes must be submitted against the lowest maintained branch where they apply   (lowest branches are regularly merged to upper ones so they get the fixes too). - Features and deprecations must be submitted against branch 4.4. - Legacy code removals go to the master branch.-->When using `bootstrap_3_layout.html.twig` form theme, the help blocks are not rendered.```twig{% form_theme form 'bootstrap_3_layout.html.twig' %}{{ form_start(form) }}  {{ form_row(form.some_field) }} {# <-- no help text is rendered #}{{ form_end(form) }}```Commits-------ff5517e Add missing rendering of form help block.