I'm trying to setup a bitbucket pipeline to elastic beanstalk for my flask app, but, the app requires several python packages not provided by the aws eb instance by default. I have a requirements.txt file and I want to have pip install the necessary packages from said file before running the application in the EC2 instance. Is there a way I can do this using the bitbucket-pipeline.yml file? If not, is there another solution to this problem?