Redis returns byte-like object instead of string so flanker crashes

[hoppla20]

After installing redis flanker crashes when I try to validate an address for the second time with following error logs:

Traceback (most recent call last):
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 2464, in __call__
    return self.wsgi_app(environ, start_response)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 2450, in wsgi_app
    response = self.handle_exception(e)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 1867, in handle_exception
    reraise(exc_type, exc_value, tb)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 2447, in wsgi_app
    response = self.full_dispatch_request()
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 1952, in full_dispatch_request
    rv = self.handle_user_exception(e)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 1821, in handle_user_exception
    reraise(exc_type, exc_value, tb)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/_compat.py", line 39, in reraise
    raise value
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 1950, in full_dispatch_request
    rv = self.dispatch_request()
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flask/app.py", line 1936, in dispatch_request
    return self.view_functions[rule.endpoint](**req.view_args)
  File "/data/workspace/campusjaeger/mailgun-microservice/emailValidation.py", line 27, in checkMail
    parsedAddress = address.validate_address(addressValue)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flanker/utils.py", line 64, in wrapper
    return_value = f(*args, **kwargs)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flanker/addresslib/address.py", line 322, in validate_address
    plugin = plugin_for_esp(exchanger)
  File "/data/workspace/campusjaeger/mailgun-microservice/env/lib/python3.6/site-packages/flanker/addresslib/validate.py", line 129, in plugin_for_esp
    if grammar[0].match(mail_exchanger):
TypeError: cannot use a string pattern on a bytes-like object

After tracing the error I found out, that the lookup_exchanger_in_cache method in validate.py returns a byte instead of a string.
I fixed the issue by adding decode_response=True in the redis_driver.py in line 18:

# replaced
self.r = redis.StrictRedis(host=host, port=port, db=db)
# with
self.r = redis.StrictRedis(host=host, port=port, db=db, decode_responses=True)

But I don't want to change files in the plugin so I wanted to ask whether anybody else experienced this error.

[hoppla20]

I just saw, that that this is a duplicate to #31