code: def get_dock_json(self):
          
          env_json = self.build_json['spec']['strategy']['customStrategy']['env']
          try:
              p = [env for env in env_json if env["name"] == "ATOMIC_REACTOR_PLUGINS"]
          except TypeError:
              raise RuntimeError("\"env\" is not iterable")
          if len(p) <= 0:
              raise RuntimeError("\"env\" misses key ATOMIC_REACTOR_PLUGINS")
          dock_json_str = p[0]['value']
          dock_json = json.loads(dock_json_str)
          return dock_json
docs: return dock json from existing build json