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Solve the following problem using Python, implementing the functions described below, one line at a time
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Description:
 def run(self):
 """ get json with build config from path """

        path = self.path or CONTAINER_BUILD_JSON_PATH
        try:
            with open(path, 'r') as build_cfg_fd:
                build_cfg_json = json.load(build_cfg_fd)
        except ValueError:
            self.log.error("couldn't decode json from file '%s'", path)
            return None
        except IOError:
            self.log.error("couldn't read json from file '%s'", path)
            return None
        else:
            return self.substitute_configuration(build_cfg_json)