Pushing picture to gitlab with python-gitlab

Question

I am trying to push a jpg picture to a gitlab repo with python-gitlab. My code looks like

gl = gitlab.Gitlab(GITLAB_URL, PRIVATE_TOKEN)
project = gl.projects.get(PROJECT_ID)

with open(file_path, 'rb') as f:
  file_content = f.read()

branch = project.branches.get('main')

project.files.create(
  {
    'file_path': f"{REPOSITORY_PATH}/{PATH_IN_REPO}",
    'branch': branch.name,
    'content': file_content,
    'commit_message': commit_message
  }
)

With (hopefully) obvious meaning of the variables. I am getting an error

UnicodeDecodeError: 'utf-8' codec can't decode byte 0xff in position 0: invalid start byte

that I suspect is related to the way I am opening the jpg file. Hints?