Add flit

Author: fkrull

Dockerfile

@@ -7,15 +7,21 @@ RUN . /etc/os-release && \
     apt-get update && \
     apt-get install -y \
         python-pip \
+        python-setuptools \
         python3-pip \
         python3-distutils \
+        python3-setuptools \
         \
         python2.? \
         python2.?-dev \
         python3.? \
         python3.?-dev \
         python3.?-venv \
     && \
-    pip3 install tox virtualenv && \
+    pip3 install \
+        flit \
+        tox \
+        virtualenv \
+    && \
     apt-get --purge autoremove -y gnupg && \
     rm -rf /var/cache/apt/lists

README.md

@@ -20,4 +20,8 @@ The image is based on the [buildpack-deps image](https://hub.docker.com/_/buildp
 * Python 3.8
 * Python 3.9
 
-This includes the header packages (`pythonx.y-dev`), venv, and distutils where applicable. In addition, tox and virtualenv are pre-installed.
+The following additional Python development tools are installed:
+
+* [flit](https://flit.readthedocs.io/)
+* [tox](https://tox.readthedocs.io)
+* [virtualenv](https://virtualenv.pypa.io/)