Issue #372: Feed doesn't work: "TypeError: sequence item 0: expected a bytes-like object, int found") (conservancy/kallithea)

[zwarmapapa]

New issue 372: Feed doesn't work: "TypeError: sequence item 0: expected a bytes-like object, int found")
https://bitbucket.org/conservancy/kallithea/issues/372/feed-doesnt-work-typeerror-sequence-item-0

zwarmapapa:

When clicking on the feed button on a repo, it will show an error page, and a WebApp Error email will be send. 

The error is:

```
TRACEBACK:
Traceback (most recent call last):
  File "/usr/local/lib/python3.6/site-packages/tg/appwrappers/session.py", line 71, in __call__
    response = self.next_handler(controller, environ, context)
  File "/usr/local/lib/python3.6/site-packages/tg/wsgiapp.py", line 243, in _dispatch
    return controller(environ, context)
  File "/etc/kallithea/source/kallithea/lib/base.py", line 536, in __call__
    return super(BaseController, self).__call__(environ, context)
  File "/usr/local/lib/python3.6/site-packages/tg/controllers/dispatcher.py", line 118, in __call__
    response = self._perform_call(context)
  File "/usr/local/lib/python3.6/site-packages/tg/controllers/dispatcher.py", line 107, in _perform_call
    r = self._call(action, params, remainder=remainder, context=context)
  File "/usr/local/lib/python3.6/site-packages/tg/controllers/decoratedcontroller.py", line 129, in _call
    output = controller_caller(context_config, bound_controller_callable, remainder, params)
  File "/usr/local/lib/python3.6/site-packages/tg/controllers/decoration.py", line 21, in _decorated_controller_caller
    return application_controller_caller(tg_config, controller, remainder, params)
  File "/usr/local/lib/python3.6/site-packages/tg/configurator/components/dispatch.py", line 114, in _call_controller
    return controller(*remainder, **params)
  File "/etc/kallithea/source/kallithea/controllers/feed.py", line 130, in atom
    return self._feed(repo_name, feeds.AtomFeed)
  File "/etc/kallithea/source/kallithea/controllers/feed.py", line 126, in _feed
    return _get_feed_from_cache(repo_name, feeder.__name__)
  File "/usr/local/lib/python3.6/site-packages/beaker/cache.py", line 601, in cached
    return cache[0].get_value(cache_key, createfunc=go)
  File "/usr/local/lib/python3.6/site-packages/beaker/cache.py", line 322, in get
    return self._get_value(key, **kw).get_value()
  File "/usr/local/lib/python3.6/site-packages/beaker/container.py", line 380, in get_value
    v = self.createfunc()
  File "/usr/local/lib/python3.6/site-packages/beaker/cache.py", line 597, in go
    return func(*args, **kwargs)
  File "/etc/kallithea/source/kallithea/controllers/feed.py", line 120, in _get_feed_from_cache
    description=''.join(self.__get_desc(cs)),
  File "/etc/kallithea/source/kallithea/controllers/feed.py", line 71, in __get_desc
    raw_diff = cs.diff()
  File "/etc/kallithea/source/kallithea/lib/vcs/backends/git/changeset.py", line 236, in diff
    context=context))
TypeError: sequence item 0: expected a bytes-like object, int found
```

Using the latest currently available version/commit \(https://bitbucket.org/conservancy/kallithea/commits/ece8fbe51ef8cb8f061845e02137808f50f125ef\). 

‌