To fetch bugs from a Jira project one can use the the fetch.py script. As an example one can use the Jenkins project to get issues from. Their Jira board contains issues that could be linked to bugs.
The fetch.py script has been executed in a Unix environment and has known issues on Windows and it is therefore recommended to run this on either Linux or Mac.
So to fetch issues from Jira, execute:
python fetch.py --issue-code JENKINS --jira-project issues.jenkins-ci.org
The --issue-code argument points to which project to fetch issues from, like in this example the project JENKINS. In Jenkins, there are several project that can be found here.
The --jira-project argument then points to jira project url. Note that the url should provided without the https:// prefix.
The produced result are then located in ./issues, aka the same directory as the fetch.py script itself where all issues are split into files of 1000 issues each. One can find some finished results in the data directory.