I have same problem and fixed.
This problem occurs when there have been changes like force-pushes to
a git repo which is referenced in a Gemfile.The solution is is to comment that gem line in Gemfile, run bundle,
uncomment it and bundle again. Then the Gemfile.lock will reference a
valid git revision.
Found in this link https://semaphoreci.com/docs/fail-could-not-parse-object.html