Force docker-compose build to upgrade setuptools

By default the image comes with setuptools==33.1.1. But pywikibot
requires that setuptools>=40.1.0 be installed BEFORE pip tries to
install it. Pin it to 49.3.0 since 50.0.0 seems to be broken for python 3.5
pypa/setuptools#2352.

Added the `pip --version` command since the `pip install --upgrade pip`
command otherwise seems to have no effect.

Change-Id: I1583ae92084dd84f12359a8f3fcfdfb72214f1af

conf/Dockerfile.bot

@@ -4,7 +4,9 @@ RUN apt-get update && \
 	apt-get clean
 RUN rm -f /usr/bin/python && ln -s /usr/bin/python3 /usr/bin/python
 RUN rm -f /usr/bin/pip && ln -s /usr/bin/pip3 /usr/bin/pip
+RUN pip --version
 RUN pip install --upgrade pip
+RUN pip install setuptools==49.3.0
 ADD requirements.txt requirements.txt
 RUN pip install --ignore-installed -r requirements.txt
 WORKDIR /code