document use of mypy

diff --git a/docs/develop/Development-Environment.md b/docs/develop/Development-Environment.md
index 3cda610edeccaeb355bbd5420fc2f76f0bc9bc7e..9abfae3765d049a040b2e61e8fe08ed5538f59fa 100644 (file)
--- a/docs/develop/Development-Environment.md
+++ b/docs/develop/Development-Environment.md
@@ -33,6 +33,7 @@ It has the following additional requirements:
 * [phpunit](https://phpunit.de) (9.5 is known to work)
 * [PHP CodeSniffer](https://github.com/squizlabs/PHP_CodeSniffer)
 * [Pylint](https://pylint.org/) (CI always runs the latest version from pip)
+* [mypy](http://mypy-lang.org/) (plus typing information for external libs)
 * [pytest](https://pytest.org)
 
 The documentation is built with mkdocs:
@@ -50,9 +51,10 @@ To install all necessary packages run:
 
 ```sh
 sudo apt install php-cgi phpunit php-codesniffer \
-                 python3-pip python3-setuptools python3-dev pylint
+                 python3-pip python3-setuptools python3-dev
 
-pip3 install --user behave mkdocs mkdocstrings pytest
+pip3 install --user behave mkdocs mkdocstrings pytest \
+                    pylint mypy types-PyYAML types-jinja2
 ```
 
 The `mkdocs` executable will be located in `.local/bin`. You may have to add