No module named 'pip._internal' on startup about bt-mqtt-gateway HOT 5 CLOSED

Starting
Traceback (most recent call last):
  File "./gateway.py", line 30, in <module>
    manager.register_workers(settings['manager']).start(mqtt)
  File "/home/pi/bt-mqtt-gateway/workers_manager.py", line 34, in register_workers
    module_obj = importlib.import_module("workers.%s" % worker_name)
  File "/usr/lib/python3.4/importlib/__init__.py", line 109, in import_module
    return _bootstrap._gcd_import(name[level:], package, level)
  File "<frozen importlib._bootstrap>", line 2254, in _gcd_import
  File "<frozen importlib._bootstrap>", line 2237, in _find_and_load
  File "<frozen importlib._bootstrap>", line 2226, in _find_and_load_unlocked
  File "<frozen importlib._bootstrap>", line 1200, in _load_unlocked
  File "<frozen importlib._bootstrap>", line 1129, in _exec
  File "<frozen importlib._bootstrap>", line 1471, in exec_module
  File "<frozen importlib._bootstrap>", line 321, in _call_with_frames_removed
  File "/home/pi/bt-mqtt-gateway/workers/thermostat.py", line 5, in <module>
    from workers.base import BaseWorker
  File "/home/pi/bt-mqtt-gateway/workers/base.py", line 11
    return '/'.join([self.topic_prefix, *args])
                                           ^
SyntaxError: can use starred expression only as assignment target