Bulk update project key with branches

Feedback

The concerned WS is api/projects/bulk_update_key. During my test it's called with the following query: project=project_key&from=io.sonarsource&to=com.sonarsource&dryRun=false and the response is:
{"errors":[

{"msg":"Malformed key for 'com.sonarsource.burgr:burgr:BRANCH:test/hirle/BURGR-235'. Allowed characters are alphanumeric, '-', '_', '.' and ':', with at least one non-digit."}

]}

Seems like it has something to do with branches, doing the same on another project who doesn't have any branch works correctly.