Prevent leaving pip install cache in Docker iamge (#7544)

* Prevent leaving pip install cache in Docker iamge

Use `--no-cache-dir` with `pip install` in Dockerfile to prevent cache
and minimize the Docker image.

Co-authored-by: Pierre Sassoulas <pierre.sassoulas@gmail.com>

Dockerfile

@@ -2,6 +2,6 @@ FROM python:3.10.0-alpine3.15
 
 COPY ./ /tmp/build
 WORKDIR /tmp/build
-RUN python -m pip install . && rm -rf /tmp/build
+RUN python -m pip install --no-cache-dir . && rm -rf /tmp/build
 
 ENTRYPOINT ["pylint"]

doc/whatsnew/fragments/7544.other

@@ -0,0 +1,3 @@
+Prevent leaving the pip install cache in the Docker image.
+
+Refs #7544