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.

assigned to @nbarry10

mentioned in commit 73c51ffd

merged