Mention coverage

Author: hynek

.github/PULL_REQUEST_TEMPLATE.md

@@ -5,19 +5,25 @@ Please tell us what your pull request is about here.
 
 # Pull Request Check List
 
-This is just a friendly reminder about the most common mistakes.  Please make sure that you tick all boxes.  But please read our [contribution guide](https://github.com/python-attrs/attrs/blob/main/.github/CONTRIBUTING.md) at least once, it will save you unnecessary review cycles!
+This is just a friendly reminder about the most common mistakes.
+Please make sure that you tick all boxes.
+But please read our [contribution guide](https://github.com/python-attrs/attrs/blob/main/.github/CONTRIBUTING.md) at least once, it will save you unnecessary review cycles!
 
-If an item doesn't apply to your pull request, **check it anyway** to make it apparent that there's nothing left to do.  If your pull request is a documentation fix or a trivial typo, feel free to delete the whole thing.
+If an item doesn't apply to your pull request, **check it anyway** to make it apparent that there's nothing left to do.
+If your pull request is a documentation fix or a trivial typo, feel free to delete the whole thing.
 
 - [ ] Added **tests** for changed code.
+  Our CI fails if coverage is not 100%.
 - [ ] New features have been added to our [Hypothesis testing strategy](https://github.com/python-attrs/attrs/blob/main/tests/strategies.py).
 - [ ] Changes or additions to public APIs are reflected in our type stubs (files ending in ``.pyi``).
     - [ ] ...and used in the stub test file `tests/typing_example.py`.
 - [ ] Updated **documentation** for changed code.
     - [ ] New functions/classes have to be added to `docs/api.rst` by hand.
     - [ ] Changes to the signature of `@attr.s()` have to be added by hand too.
-    - [ ] Changed/added classes/methods/functions have appropriate `versionadded`, `versionchanged`, or `deprecated` [directives](http://www.sphinx-doc.org/en/stable/markup/para.html#directive-versionadded).  Find the appropriate next version in our [``__init__.py``](https://github.com/python-attrs/attrs/blob/main/src/attr/__init__.py) file.
+    - [ ] Changed/added classes/methods/functions have appropriate `versionadded`, `versionchanged`, or `deprecated` [directives](http://www.sphinx-doc.org/en/stable/markup/para.html#directive-versionadded).
+          Find the appropriate next version in our [``__init__.py``](https://github.com/python-attrs/attrs/blob/main/src/attr/__init__.py) file.
 - [ ] Documentation in `.rst` files is written using [semantic newlines](https://rhodesmill.org/brandon/2012/one-sentence-per-line/).
 - [ ] Changes (and possible deprecations) have news fragments in [`changelog.d`](https://github.com/python-attrs/attrs/blob/main/changelog.d).
 
-If you have *any* questions to *any* of the points above, just **submit and ask**!  This checklist is here to *help* you, not to deter you from contributing!
+If you have *any* questions to *any* of the points above, just **submit and ask**!
+This checklist is here to *help* you, not to deter you from contributing!