def _WorkerCommand_environment(self):
        """Return list of shell commands to prepare the environment for
           bootstrap."""
        worker = self.workersArguments
        c = []
        if worker.prolog:
            c.extend([
                "source",
                worker.prolog,
                "&&",
            ])
        if worker.pythonPath and not self.isLocal():
            # Tried to make it compliant to all shell variants.
            c.extend([
                "env",
                "PYTHONPATH={0}:$PYTHONPATH".format(worker.pythonPath),
            ])
        elif worker.pythonPath and self.isLocal():
            # Tried to make it compliant to all shell variants.
            c.extend([
                "env",
                "PYTHONPATH={0}:{1}".format(
                    worker.pythonPath,
                    os.environ.get("PYTHONPATH", ""),
                ),
            ])
        return c
Return list of shell commands to prepare the environment for
           bootstrap.