Integrate bash script

Ok, this should be all we need to integrate the new bash script.

• Installs bash and git in the container
• Calls the bash script from python if the API returns a 403 (user doesn't have permission to merge). The exit code of this script is then used.
• Added set -e to the bash script so that if any command fails the script doesn't exit with a status of 0
• Added an if statement to use a different source SHA when running as a special Merge Request Pipeline.
• Updated requirements file to use latest versions of packages. I included all dependencies this time as there seems to be a conflict with the urllib3 package otherwise.

merge-request-check/Dockerfile

@@ -14,9 +14,12 @@ LABEL org.label-schema.build-date=$BUILD_DATE \
 RUN mkdir /code
 WORKDIR /code
 
+RUN apk add --no-cache bash git
+
 COPY requirements.txt ./
 RUN pip install --no-cache-dir -r requirements.txt
 
 COPY approval_check.py ./
+COPY merge_review_check.sh ./
 
 CMD ["python", "approval_check.py"]